I find that writing a guide for a game is always a thrilling experience, especially if the game in question has no guides whatsoever. Here's hoping that this will be the first of many guides for this game!

Speaking of the game, all of the achievements (except one) are straight-forward: there are no vague hints, cryptic descriptions or hidden achievements; nevertheless, a guide may still prove useful in providing aid to those in need. Also, since every mission is repeatable, there are no missable achievements, and, apart for those achievement tied to a specific difficulty level, you can obtain every achievement even on the easiest difficulty, so if you can't complete an achievement on the first try, try to lower the difficulty level.

As a final note, I've tried to obtain every achievement the earliest I could, but I believe some of them (one or two more than those in the Trivial section) can be naturally earned while playing normally. I'll list my method anyway, just keep in mind that it may not be the cushiest one.

These achievements require no effort whatsoever and will be acquired automatically while playing.

Efficient
Kill 3 or more enemies with a multi-attack ability.


You’ll obtain this one automatically during the prologue after using the Mage’s “Pwah!” ability.

Super Special
Obtain an item of Mystic quality.


Mystic items have a yellow/golden outline when inspected in the inventory; they are not so rare and drop quite often, especially on harder difficulties: I personally got this one just after finishing the first Story quest in the game.

Mystic Run
Complete a quest with a party of 4 or more that have Mystics in every slot.


As said before, Mystic items have a golden/yellow outline in the inventory; you’ll need to accumulate quite a lot of them before being able to tackle on this achievement. Regarding equipment, you have to know that the equipment in the game is limited: each item exists only in one copy, and in one copy only, and once you have obtained all the possible equipments, enemies will only drop consumables once defeated, so just keep killing enemies until you get enough Mystics.

Kick the Bucket
Defeat all dummies in a Training quest.


Self-explaining: defeat all the dummies during a Mini quest, you don’t even need to exit the training range to get the achievement.

High Roller
Have 16 or more dice roll at once.


You should obtain this one automatically during the last encounter of the Story quest “Taking Stocks”, the first turn after the appearence of DragonboneBolt and his reinforcements, assuming all of your heroes are alive.

Super Heroes
Kill 50 or more enemies in a single encounter.


You should eventually get this one without even noticing, since later quests are filled with enemies. If you want to obtain it early, the earliest you can do it is in the second Story quest, “The Graveyard Shift”: don’t rescue any villagers and the skeletons will keep on spawning. Altough they are fairly easy to kill, they can easily outnumber you, and if you rescue a villager, they might try to kill them (even a single villager’s death means game over, so leave those villagers lying on the ground, it’s for their own sake); for these reasons, you may want to try this achievement after you’ve obtained some better equipment to increase your success rate.
You can also wait until the Story quest “Taking Stocks”: in the last encounter you have to kill thirty enemies to summon the boss, who will appear along with two group of enemies, leaving you with plenty of enemies to kill (just make sure to not kill the boss prematurely).

Let’s Try That Again…
Lose a hero to a training dummy.


You can obtain this one very easily just after the Prologue, by playing the “Training – Close Combat” Mini quest: just put the Ranger between some dummies and end turn repeatedly until the dummies overthrow her. Be sure to remove any equipment granting armour from your hero.

Paunch it!
Complete a quest with a party of 3 or more without weapons.


You can obtain this one easily as soon as after the first Story quest, by playing the “Training – Mixed” Mini quest: select the Fighter, the Rogue, the Barbarian and the Ranger, by making sure all of them have no weapon equipped (other equipments are fine, especially equipments that grant attack boosts; they are extremely useful). Your characters will be limited to one melee attack option (“Paunch it!”) for a terrific one point of damage (which can hovewer be boosted by dices at the start of the turn or by other means). You’ll need to destroy every dummy on the battlefield: the simple ones will go down in one hit, but the armoured ones will require you to remove their three armour points and attack them in the same turn, since armour regenerates in between turns.

It Takes A Village...
Have villagers deal 6 or more damage in a single campaign encounter.


Self-Help
Win a campaign encounter with only villagers remaining.


You can obtain these two achievements in the same Bounty quest, “Farmers Strike Back”, unlocked after completing the first Story quest. Select a powerful but not armoured hero, like the Ranger, and try to group all of your units in the center of the map, at the southern exit of the barn, placing the hero to the right of it in order to block the eastern Ironscale. Your villagers are incapable of doing damage on their own, hovewer they can be boosted by the dices rolled at the start of the turn, or by the village elder: he is your most important unit as he can heal all allies around him and boost the movement, armour or attack of two units; keep him at the center of your group in order to protect him (he can’t heal himself), and boost and heal your villagers accordingly. If you lose even a single Villager, the mission is lost, so try to keep them alive and spread aggro between them. The majority of the enemy units have one or two hit points at max, hovewer, there are two Ironscales who can be quite problematic: they can pack a punch and are armoured, so try to use your hero to defeat them while your villagers defeat the weaker units (this will eventually grant you the first achievement). Rember to leave at least one enemy unit alive, and have it kill your Hero (you don’t want an armoured hero since their armour would regenerate every turn, making killing them very difficult if not impossible), then kill it to finish the mission and get the second achievement.

Consul's Most Wanted
Reach maximum Aggro on all heroes in a party of 4 or more.


Each time an hero kills an enemy, it gains aggro points: the more powerful the enemy, the more aggro accrued; each time an enemy attacks an hero, the hero loses one aggro point. Aggro is saved between turns but not between encounters. The maximum aggro points an hero can rack up is nine. That said, there are some consumables that increase aggro, along with some equipments that grant an increase in aggro each turn: you can stack up these consumables and use them in bulk, or try to kill as many enemies as necessary while avoiding getting hit (leaving a spawner standing to increase the number of enemies present would be ideal) to complete this task.

Mass Consumer
Use 60 consumables in a single encounter.


Gladiator
Win an encounter after 40 rounds.


Make sure to bring enough consumables with you; you’ll need at least the three-spaced bag.; you can use one item for every one of your unit’s turns.
During the Mini quest “Curfew Roundup”, unlocked after the fifth Story quest, you’ll need to search for two shacks and then bring all of your heroes and villagers to the exit zone. Group of enemies will spawn after reaching certain parts of the map, but after eliminating them you will be left alone. Simply end turn while using items until you reach the needed amount of turns and then complete the quest.

Kingslayer
Kill 5 or more Minibosses in a single encounter.


The Bounty quest “Unwanted guest” starts with an ogre already present on the map, and two spawners: the one nearest to your starting position spawns a group of three enemies, and should be your top priority, while the farthest one spawns an ogre every ten turns (plus another one once destroyed); clear the map as soon as possible leaving that spawner standing, and you’ll get the achievement after killing the fifth ogre, no need to complete the mission.

Seven In One Blow!
Kill 7 or more enemies in a single attack.


For this one you’ll need an hero capable of attacking at least in a 3x3 grid, like the mage or the cleric equipped with a staff, or the paladin with an hammer, and an hero equipped with trinkets granting the Attraction effect (this is not mandatory but makes things easier). The earliest you can get this one is during the Story quest “ The Graveyard Shift”: let a bunch of skeletons spawn, concentrate them in a grid using the Attraction ability and let the mage finish them. Another way to accomplish this feat is during the last encounter of the “Taking Stocks” Story mission: use three armoured heroes to block the breach in the palisade at your starting position, and let the enemies pile up before killing them; the starting enemies should be weak enough to get one-shotted by the fire attack.

Firefighting
Have 25 or more squares on fire simultaneously.


The cleric, the mage and the sorceress can equip staves that can apply the “Tile Fire” effect (do not use “Fire” effect staves) for a certain number of turns over an area, firing it up; the weakest staves apply fire on a 3x3 area for two turns. Just equip two or more heroes with these staves and attack random tiles on the map (try to avoid unpassable tiles as they can’t catch fire) for two consequential turns and you’ll get the achievement.

Master Of Disaster
Complete an Xtreme multi-encounter quest with no hero deaths.


You don’t need to complete the whole quest, just completing the first encounter without losing any hero will get you the achievement. Make ample use of potions and other objects, you are not restricted like the “Thirsty much?” achievement; the earliest you can do this achievement is in the third Story quest “Supply and Command”.

Personal Space
Complete a quest with a party of 4 or more equipped with only melee weapons.


Keep Your Distance
Complete a quest with a party of 4 or more equipped with only ranged weapons.


You can obtain both of these achievements by playing the Mini quest “Training – Mixed” and equipping the proper weapons.
Note that for the purpouse of the ranged achievement, staves do not count as ranged, only bows and crossbows do; considering this, the earliest you can obtain the melee achievement is just after the first Story quest, provided you have a dagger for both the ranger and the rogue, while you’ll have to wait for the warden for the ranged one, provided you can equip both the warden and the fighter with crossbows, and both the ranger and rogue with bows.

Tenacious
Win an encounter having lost 4 heroes.


As the achievement states, you need to complete a single encounter, not the whole quest, after losing four or more heroes. Since heroes return with diminished health in between encounters durin a multi-encounter quest, you can just let four heroes die by placing them amidst enemies and then complete the encounter without any impact on the whole quest.

Thirsty Much?
Complete a multi-encounter quest on Veteran or higher without using potions.


It seems the wording on this one is incorrect: you must not use any consumable at all: so don’t equip any in the guild hall and select your preferred multi-encounter quest (the earliest one is “Supply and Command”, the third Story quest); the achievement will pop after completing the last encounter on the quest.

About To Have A Bad Time...
Have a skull assigned to 6 or more heroes in a round.


Start the Bounty quest “The Long Road”: if on the first turn there are six or more skull dices, try to grab them before the enemy. If the enemy is faster, or if there are not enough dices, simply restart until you succed. The achievement will pop as soon as the last skull is assigned, no need to start the the turn.

There Can Only Be One!
Have a hero defeat themselves in combat.


The icon on this one is a huge hint for an otherwise puzzling achievement. I’ll explain how to obtain it but beware that it spoils part of the seventh Story quest, “Score Settling” and part of the tenth Story quest, “Monastery Mystery”.
The earliest you can obtain the achievement is in last encounter of “Score Settiling”; the quest ends with a boss battle with Snapjaw, an armoured and quite strong kobold; after defeating him, he will join your party. You’ll have to replay the quest with your newly acquired hero and make sure that he lands the killing blow on his evil alter-ego. Since the quest is quite long, you may want for the “Score Settling” Story quest, when, during the first encounter, you’ll have to fight the Assassin, who will then join your team like Snapjaw. Just like Snapjaw, have the Assassin land the killing blow on her evil alter-ego.

Casually Completed
Complete the final campaign quest on Casual or higher.


Took It Easy
Complete the final campaign quest on Easy or higher.


Achieved Normality
Complete the final campaign quest on Normal or higher.


Virtually Veteran
Complete the final campaign quest on Veteran or higher.


With Xtreme Prejudice
Complete the final campaign quest on Xtreme.


I strongly suggest to complete most, if not all, of the secondary quests before attempting the quest on Xtreme, both to gain knowledge of every hero's abilities and usefulness, and to obtain equipment.
For this task, you'll want at least two heroes with healing capabilities, and as much heroes as you can with armour piercing abilities. You'll have to select ten heroes in two groups: a group of seven and a group of three. Get an healer and an armour piercer on both groups, plus an hero with strong defensive capabilities on the smaller group (the Knight with proper gear granting him counter-attack abilities can both function as a tank and a piercer, making things easier). The quest is composed by five encounters.

First encounter: you'll have to destroy a spawner with your main group of heroes; advance slowly, focusing on the Dust Mages and Armoured Knights. Enemies’ groups appear once you reach the spawner and after destroying it (first one behind the grave, second and third on the right and left). You’ll have to split the group after this: one hero will join the group at home, the other will continue on their path. Select that one hero carefully, he'll have to fight armoured enemies.

Second encounter: You'll have to destroy two spawners with your main group, each spawner when destroyed summons a mid-boss and weaker troops. The only real menace here are the starting Dust Mages and Armoured knights, try not to get blocked on the narrow bridges while moving from one spawner to the other.

Third encounter: You'll have to kill three witches with your main group. Keep an eye on every blue dice at the start of the turn. If the enemy manages to get even a single blue dice, do not attack any of the witches: blue dices grant them the ability to summon armoured knights when attacked (altough sometimes they may still summon them even with no dice assigned). After killing the witches, you’ll have to survive for two more turns, so you can’t just suicide rush them. Defend one of the two starting zones by concentrating all your heroes there, and let the enemies come to you: focus on the Dust Mages first as usual, and attack everyone who comes near. Prioritize the witches ONLY if they are in range of your units and ONLY if you are sure that they have no blue dices.

Fourth encounter: The toughest encounter, you'll have to defeat every enemy on the map (two more groups will spawn) with the second (and smaller) group. Don’t let the enemies swarm you, try attack, heal and move. Beware of the Ironmages, they can heal nearby troops when attacked if they get the skull dice, so try to ignore them if possible. The Knight is really useful here as the space is very limited and the enemies will eventually encircle you, but with the proper gear he can both stall them and counterattack for free, possibly with piercing damage.

Fifth encounter: This is probably the easiest encounter, you'll have to defeat four Golems with all of you heroes. The golems are heavily armoured and have staggering health, but are not so though. Concentrate on one at a time and they will fall quickly, your heroes should be powerful enough by now.

08/01/2022: Guide created.