Rot:
it's hard to kickstart it but once you've got some it gets easier. Don't start a game thinking you'll go rot, instead do it if you have a good opportunity, ie. no one else is credibly going to compete with you on that, you are guaranteed to get 3+ rot without going out of your way to (try to) get killed by corrupted birds.

For one having enough corruption allows to get corruption as quest reward. Not good but if you need a bit more... it's an option. Also once you hit 5 corruption killing the corrupted birds increase corruption. Given you'll get a lot of dice it makes it possible for casters to beat them, but also kill the king, which is the most reliable way to win the game. There's also more to it, like failing on purpose some perils.

It works best as spell casters, because you get the most rot cards in the deck and you will want to draw a lot of spell cards as there's a bunch of bad cards but also some of the best in the game.

The 1 damage in the morning is not that bad, you will aim to hold healing items so whenever your HP goes low you should be able to fix it. It can even help as dying is a way to quest faster by respawning closer. Like do a quest at night, finish the day with 1 HP and given you know quests alternate being close or far from the starting location you'll save up a turn or two. Much more annoying is being unable to go through the stone circles.

Quest reward:
The item reward of quest is the least important part. The driving factor with quests is the stat boost. Excess in any stat makes it pointless. High fight without body will die to a spell. If it lacks wits it will never draw the best items, fail perils, can't burn cards to guarantee dice rolls. and hoard game wining cards (rot whine, teleport, banish, etc). If you want to increase your odds, items or spells to boost your odds will help.

Followers:
Followers are pretty rare, few of them are really good. Your best bet is to play Scarlet, otherwise it's rarely an important factor, although a few combos are really potent like Brun with an apprentice.

Bad spells:
Not being able to cast some spells isn't an issue. If you don't want something, burn it. That's how you should use most cards, the overall quality of cards in the deck vary a lot so you want to draw a lot to get the best ones. If you draw in the spell deck, you should have a result in mind. 3 spirit will unlock a lot of good options, it's probably not worth if you have less. 4 will let you cast most things that matter. It's good enough a lot of the time. Also items can increase it. Burn cards to get rid of what you want, but also burn cards to get the dice roll you want. Once you start doing this you'll renew a lot your hand so you'll get a lot of cards you actively don't want to play as you only have so much gold/mana so having a card you can not/do not want to play is kind of routine.

Spell deck is great:
As part of your basic hero loadout you want good items. It may take a while if you don't draw good options, but once you have a good loadout, what will you do? You can keep drawing to get a rot whine. It's... Great on its own, but that should take a while to happen. Trickery isn't terrible but it pales in comparison to what spells offer. Teleport, banish, kill opponents or yourself to quest faster and delay the enemy but also get rid of anybody breaking into the castle, give yourself various buff, move faster on the map etc. A caster can and should quest faster than anybody else. You don't need lots of fight as an opponent taking a detour to beat you up will often times delay his own questing to maybe not beat you up and even risk being beaten up himself.

Declarations:
Being prestige leader is better than not being prestige leader, however the declarations aren't super useful generally speaking. I like aiming for it as say Scarlet for niche interactions like the one where the guards mess with cities as an easy way to use her power for followers but most of the time I don't care. It's just fun to be the prestige leader, but it's not very useful.

There are rings and amulets that help you start out with rot.

Once you get to about 3 rot the game starts feeding you more and more rot. There are random events, and your quests will all start giving you rot. There are also items that can give you rot when equipped. Once you are corrupted, every Bane you kill will add you another rot and every kill at all will heal you a health point. So once you hit 5 rot you can snowball very quickly.

I will say, this game is amazing and well balanced in my opinion. When you get a good lobby there is almost not game quite like it. I would like to give people the ability to draw specific cards at spawn in and not just get random cards as that can crush some builds.

It is a little short, sometimes I feel like if you get 2 bad deaths you are more or less out of the game unless you have a build that can rack up prestige through kills (and you just defend the king).

I would like to see the devs make leveling unlocks a lot faster and put the game out for free or for 80% off to try to get more people playing as I STILL love playing this game. I just had 2 games over the last weekend.