You reach Upper Avernum by taking the south exit from Fort Emergence. I recommend checking out the XP pool, dealing with the goblins and raiders, then exploring the rest of the area in a clockwise order. The Sliths, Chiturachs and Dangerous Lizards are probably too dangerous for you on your first visit into the area (come back after you've dealt with two plagues, with the Orb in your possession)

Also, I've actually marked the starting location of most hidden passages for Upper Avernum (rather than just where the passages lead), but I expect they're obvious enough that you'll be able to spot them yourself elsewhere.

North of Fort Emergence
X407Y437 – XP granting pool.




North of Bandit Lair
X421Y413. Hidden Passage leading to Razordisk x6.



West of Fort Emergence
X402Y477 Hidden passage to Iron Shortsword.



North-West of Fort Emergence.
X408Y454. Hidden passage to body with Thereza's lost papers, guarded by Giant Lizards.


South-West of Ghikra (guarded by Thugs + Apprentice mage)
X379Y417 125 gold and 6 iron javelins.

South from New Cotra
X366Y448 - Giant Lizards guard a healing potion, scroll: Radiate Ice and crude longbow

Mushroom Patch north of Portal Fortress
X353Y441. 2 Healing Herbs

North of Portal Fortress
X339Y439 Frozen worm (quest location) - Emerald, Lovely crystal

North of Portal Fortress
X344Y350 Bronze Shield.

Hidden Passage North of Portal Fortress
X339Y416. Greater Shade guarding an Iron Shortsword

North-West of New Cotra
X340Y391. Hidden passage to big Nephil Camp (combat). 250 gold, Stability Bauble.


West of New Formello (Orb)
X341Y364.6.Fiery Wand

North-East of New Formello - Boat or Orb ride to shambler guarding a Fine Slith spear
X370Y340

South of Slith temple (Orb)
X397Y347.6.2 Spiritual Herbs

You generally want to explore the caches next to Fort Emergence, then head north and to the west around the mountains before looping around and exploring the southern side of the mountain range. If you leave the two drake encounters and Guhkbar's Pit alone the first time you're in the area, pretty much everything else is doable.

Near exit from Fort Emergence:
X52,Y414. Nature Lore 2. Healing Elixir.

Right below - Healing Herbs x3.

East of Guhkbar's Pit
X71,Y434. Nature 2. Scroll: Group heal.

West of Guhkbar's Pit
X37Y436. 2. Fiery Wand

South of Fort Emergence - Abandoned house
X98Y443 Battle with slimes, 200 gold.

North-West of Inn of Blades
X106Y400.2. Scroll – lightning

North of Inn of Blades South of Farport – hidden passage to Stone Pillar Circle
X111Y387-X114Y400 - Stone pillar circles improve your party's knowledge of priest spells. They can be visited in any order, and will teach you (from the first to the fifth): Curing, Smite, Unshackle Mind (and +1 Dexterity), Ward of Steel (and XP), Return Life. Visiting all the circles forces you into an additional combat near the endgame, but it's not very hard.

South of Farport
X129Y377.3.Terror Wand.

Soth-East of Farport, Troglo camp
X150Y365 800c, ensnaring wand, Ivory Band (2% armor, +15% MER, +5% missile damage)

East of Troglo camp, guarded by Troglo ambush
X183Y362.3.Sheilding Knife.

South of Farport, hermit hut - quest to bring messages back and forth between two hermits.
X135Y371-X138Y279

Hidden passage on the southern side of the mountain from Troglo camp (East of Hermit Hut):
X146Y375 12 steel javelins

West of Porter's Retreat X168Y389.3.Scroll: Stoneshatter

West of Porter’s Retreat
X176Y375 - Unicorns guarding Spiritual herbs x2

North of Distant Hut (Orb)
X55Y373 – Stability Girdle

North-West of Distant Hut - Dryad.
X42Y390. Requires flower from valley of flowers (below Valley of Ursagi). Tells secret item location near Calloc

North-West of Farport (Orb)
X107Y348.Bars of Iron, 2 Fine Steel

North of Fort Emergence, West of Farport (Orb)
X74Y371.3.Yew Bow.

North via Orb from the above
X69Y366 Combat with specters and vengeful ghosts. Duelists Rapier.

Way North of Pergies / West of Distant Hut
X11Y399.Bronze Broadsword.

West of Distant Hut:
X20Y420. 2. Steel breastplate.

West of Distant hut – hidden passage leads to fight with Drake and Fire Lizards
X44Y412. 900 gold, serpentskin helmet

Between Silvar and Colchis
X149Y465. 3. Sanctification scroll..

North of Silvar X138Y439. 2.Gold bar.

North of Silvar
X138Y443. Energy potion

North-West of Bolton – Hidden passage to drake lord. Help fight lesser drakes for Fibrous Breastplate. Kill for 1000 coins and another Fibrous Breasplate (you can "help" during the first fight by placing allies between you and enemies and healing them)
X210Y435

North-West of Bolton – Nephilim. Will trade a Yew bow for an Iron bar if the party contains a Nephil
X186Y428

East of Nephil camp:
X218Y409.4.Oozing Wand.

Herb Patch right south of that
X217Y414.7.Graymoldx2.

North-East of Bolton
X225Y444.4.Purging Crystal

East of Crystal - Stone Pillar Circle with Ogre Worshipers
X223Y437. Xian Skull.

A bit north of Bolton Xian skull pillar – Nephil settlement. .
X230Y427 Help them drive off Ursagi if you haven’t killed any Nephil patrols in the area. Chance to buy Nephil weapons

North of Port Townsend
X25Y303 Iron Broadsword

South of Shayder:
X9Y334.4.Scroll:Domination.

X5Y342.3.Fine steel gauntlets.

Next to Kuper
X91Y309.4.Focusing Crystal

West of the Kuper focusing crystal
X75Y311. Terror wand guarded by spiders

Directly north of Kuper – hidden passage to Stone Pillar Ring
X101Y302-X102Y295


North of Bavner, East of Kuper
X82Y309 Blessed Boots

North of GIFT lair - patch of flowers
X67Y284.6.Energetic Herbs x2

West of Northpoint Lighthouse - Gremlin combat encounter
X68Y247. Speed potion x3.

Next to Hectar:
X61Y256.5.Scroll: Acid Shower.

North West of Fenris Port – Graymold Patch
X98Y253.3. Graymold x2.

Once you're done with the Slime and Cockroach plagues, I recommend you go back to Fort Emergence and get the Orb.

Somewhere in Avernum (during Orb Quest)
X381Y321.5.Mandrake Root.

You could risk going all the way to Calloc for spell training, but the recommended order of exploration is Troglos - Ursagi - Southern Isles - Eastern Undead - Giants.

Above Sharimik
X175Y295.4. Fine Steel

South of Lorelei, north of Anama Facility
X178Y244.4.Graymoldx2

Next to Anama
X179Y253.5.Ruby

East of Anama (Orb)
X202Y258 – Focusing and Battle Crystal

South of Anama, guarded by Troglos
X202Y278. 150 gold, Crystal Woven Chitin.

Above Castle Troglo (Orb)
X224Y281.5.Fine Leather.

Hidden Passage North of Troglo temple (Party luck = at least 3)
X249Y309. Crystal: Sniper.

North of Troglo temple, but you have to take the long way around – stone circle (no spell increase)
X256Y305. Fight altered giants for 300 gold and Wand of Inferno

South of Angel's Rest (Orb)
X228Y328 - Hidden passage to Widsom Crystal

East of Gidrik (Orb)
X212Y338.4. Healing Elixir.

North of Goddale (Orb)
X219Y350 Mine - 300c, fine steel (2)

From there, (Orb) East to body
X235Y339 Momentum Gauntlets

Valley of the Ursagi
X251Y338.5.Golden Necklace.

Past the Valley of the Ursagi (Orb)
X262Y319.5.Energy Elixir

Next to Ursagi Valley:
X264Y394.5.Steel Shortsword,

Nearby - Valley of Flowers (Gremlins guard a perfect flower for Dryad next to Distant Hut)

North from there (East of Fiery Pit)
X243Y376. Mine - get 100-2000 gold (?) (varies depending on RNG? I managed to get up to 2000, and reloads changed whether combat followed or not) before eventually fighting Ursagi + Goblins

Valley of the Ursagi (North) Mine
X246Y337. Iron Halberd and 350 gold guarded by Ursagi and Goblins.

East of the mine above
X251Y338. 5. Gold Necklace.


Next to Gorst.
X329Y425.6.Battle Crystal

Warmth ring guarded by basilisks right above

Gebra:
X296Y444.6.Shield Ring.

Down on the Basilisk islands:
X250Y452. 6. Fine leather.


Very end of Basilisk Islands
X264Y468. Battle with basilisks. Tinker Gloves, 500 Gold.


Stone Pillar Circle nearby
X265Y470.2 Mandrake Roots.

North of Stormport (Orb)
X299Y375 – Stone pillar circle

North of Stormport (body)
X315Y359 Micah Band

Below Greompel’s Hut (East of Tomb of Vahkohs) (Orb)
X327Y354.6.Steel Greaves.

East of Squiggus
X325Y299.6.Ensnaring Wand

Nearby - Fine Herbs x1.
X320Y295. X328Y308

South-East of Squiggus, past Gremlin+Basilisk forest
X331Y325 - Emerald tree. 8 emeralds + gremlin combat encounter.

West of Fading Tower (Orb)
X269Y273.8. Mandrake x2

North of Softport
X126Y245. 5. Flesh Fused Greaves


North of Softport – wrecked merchant caravan
X132Y241 – Mandrake Root


Way east of Softport, Graymold patch
X178Y243. Graymoldx2


North of Softport, South of Abode hut – Nepharim guarding secret passage
X125Y250 Armor Ring.


North of Malloc (Orb)
X178Y163.7.Focusing Crystal.

West of Spineridge – Stone pillar circle
X150Y187

North of Malloc
X175Y189. Silver Necklace

North of Softport, south of Dorgnas
X101Y212.6.Scroll: Speed Burst


North of Adobe Hut
X126Y186 – Volsto the archer, archery training for 5000.

South of Dorngas
X107Y180.6. Clarity Talisman.

North of Calloc
X62Y187.3.Wand of Carrunos

West of Calloc (Orb)
X41Y197.6.Fine Leather

South of Calloc
X62Y222.6.Invulnerability Potion

South of Calloc – Tarnished Chain
X54Y216 (requires info from Dryad near Distant Hut)

South East of Calloc - Alakas colony
X73Y223 - Combat with Gazers, drop Eyestalks x1

South of there:
X77Y277. Energetic Herbs x2.

North-East from Marish
X40Y251.5. Speed Elixir

West of Wainscotting
X10Y163.7.Scroll: Return Life.

Below Lorelei
X174Y230.7.Wisdom Crystal.


North of Poulsbo (and north of Dryad grove fighting giants)
X219Y207.7.Steel Halberd

Valley of Giants
X268Y234.Healing Herbs, Graymold

Valley of Giants
X248Y228. Steel Broadsword, 50 coins.

Hidden Passage North of Spineridge – hidden passage to Stone Pillar Circle
X260Y164.

West of Spineridge
X250Y175 Gold Nuggets (5)

West of Appleton
X213Y177.7.Basilisk Fang Wand.

North of Aplleton
X234Y159.Steel Shield.

East of Bremerton - Scirbbane addled empire soldiers guarding hidden passage to scribbane production facility.
X263Y149 - if attacked, 750 gold, scribbane x4.

(Orb) South over the water from there
X260Y158.8.Speed Elixir

Maddok Island, east of Mernia
X302Y183.8.Mandrake Root.

South-East Maddok
X317Y271.7.Invulnerability Potion

North of Gale
X325Y119.9. Focusing Crystal.


West of Greendale (Orb) – Combat with Eyegazers
X266Y125 - Gazer eyestalk

West of Bremerton, past gazers and eyebeasts
X264Y115.9.Scroll: Return to Life.

North of Tevrono, East of Eastern Golem Spire, golem battle site
X301Y62. 4 lovely crystal, 3 beautiful crystal, 1 purging crystal.

Herb Patch (North East corner of map)
X292Y23.14. Healing, spiritual, energetic herbs x1.

North-East corner of the map:
X317Y25.10.Invulnerability Elixir.

North East Corner of map – Xian Vest
X314Y22. Buy for 2000 gold or kill for Dread Curse. (18% armor, +2 First Aid, +2 Magical Efficiency, +2 Lethal Blow, +2 Sniper)

Island in North-East corner of the map (Orb)
X323Y26. Combat encounter (skeletons, banshees, then Mung Demons and Hhortah). Requires harp. Ward of Elements 3.


Way east of Trevono (Orb)
X325Y60.9.Fine Steel,
Mushroom patch with 2 Spiritual Herbs nearby


West of Greendale - Deserter Camp (combat with empire troops)
X254Y108 - 300c, Slith Bloodspear (5% armor, 8% critical hit, +4% riposte)

North of Eastern Golem Spire (Orb)
X283Y42.Combat with Ur-Basilisks and Mutant Lizards. Lost Mage’s Robe.


West of Western Golem Spire
X246Y63.10.Rod of Battle.

Church of Divine Lucre
X254Y36 5000c for Return Life, Divine Retribution, Divine Restoration training, -1 reputation, Blessing of Lucre (+2% damage)
If attacked - Dread Curse, 7500c, mandrake root, fine leather, focusing crystal, fine steel, scroll: powerslash, invulnerability elixir, basilisk fang wand, Mercuric Plate (34% armor, +6% evade, -20% to hit, +1 action points, -1 Strength)

Herb patch in guild controlled area past church of Divine Lucre
X265Y8.9?. Mandrake X 2? requires knowledge or talking with a guild member?

South of the above Herb Patch
X281Y25.10.Fine Steel

North of Eagle Rock (Orb)– Alien Beasts, 250 coin
X205Y57

North East of Eagle Rock
X215Y50.10.Scroll:Powerslash

South of Eagle Rock
X210Y83. Steel Spear, 350 gold

Next to broken wall north of Bremerton
X213Y102.8. Fine Steel

East of Moon:
X186Y113.8.Energy Elixir.

North of Moon (Orb)
X146Y93. Terror Wand


Herb Patch (Orb) south of army camp south-east of Blackcrag Fortress
X213Y38.2 Healing Herbs

South of Blackcrag Fortress
X198Y35.11.Wand of Death.

Herb patch directly West of Blackcrag Fortress
X165Y9.10. Healing, spiritual, energetic herbs x1.

West of Draigoth
X157Y76.10.Wisdom Crystal

South of the Northern Footracer wall, across the river:
X130Y73.10.Invulnerability Potion

East of the lower Footracer gateway
X132Y115.8.Scroll: Speed Burst.


Below south-west corner of Footracer wall
X91Y135.8.Wand of the Inferno.

West of Dorngas - Dragon Lairs.
X90Y169 - The entrance that doesn't require an Orb. If you come here too early, you can lead the Alien Beasts to Sulfras, and she will kill them for you.

North of said entrance (Orb) - Drakes guarding Chaotic Halberd
X91Y164 - Attack for Dread Curse, Chaotic Halberd (8% armor, +10% critical ht, +2 Dexterity)

Beneath North-Western corner of Footracer wall
X33Y13.13.Bounding Band

West along the coast - Fungus Patch
X15Y17. 2 Mandrake Roots, Gazer/Eyebeast fight.

South-East of the above (Orb) - Drake Blessing (Blademaster and Spellcraft +1 for everyone)
X42Y27. Pay 5000 (or 6000 to avoid combat)

South along the coast - Gremlin Woods.
X20Y52. Several Gremlin combats, dropping Fine Wine and Radiant Greaves

West of Erox
X28Y92.9.Corrupting Baton

South of there (North of Wainscotting)
X40Y103 - Battle with Demons. 1000 gold.


West coast (west of Defiled Tomb, South of Erox) (Orb)
X18Y119.9.Rod of Defense

West of Dellskeep
X93Y45.12.Rod of Alacrity.

West of Wyvern Pass (Orb)
X120Y34.11.Energy Elixir.


Fungus Patch way north of Manara.
X108Y75.Graymold

West of above Fungus Patch
X92Y86.9.Invulnerability Elixir