Helherron Spoilers
The following information can be considered spoiler information.  Don't read on if you don't want to know this stuff.  You've been warned…
Maps
The map section is pretty rough right now.  There is a lot more information that could be added to these maps (like most of the information below), but we'll see if I end up doing that or not.

To use the maps, just hunt around with your mouse.  You should get pop up hints on some things and hot spots which will move you to other maps.  Most of the maps have white dots where the level changes happen, but not all white dots are level changes.  Anyway, if you've looked at the maps in the games at all you'll be familiar with how this works.  I did change the colors of the exits on a couple maps because they were too hard to see.
Locations
Name # of levels Notes
Odrewold town  
Goblin Cave 4  
Ancient dwarven temple 2 Hidden in forest near Goblin Cave
Kobold Cave 1  
Buglurji town  
Abandoned Farm 3  
Orc Cave 3  
Basilisk Cave 1 Hidden in mountains west of Buglurji
Witch's Hut 2  
Bee Cave 1  
Cadar town  
Ancient Tomb 2 Shows up after you get quest from Yannick
Slugmen 3  
Gitala town  
Bandit Camp 1 Shows up after you get quest from Ratchyr
Abandoned Castle (Ngidagh) 3  
Birdman Cave 2  
Castle Galatako town The town and castle levels
    Catacombs 1 Entrance is shown when you get the quest
    Wine Cellar 1  
Dwarven Mines 3 Shows up when you get the quest from the Mayor of Galatako
Dwarven Village town In Dwarven Mines
Elven Ruins 2 Shows up when you get the quest from Venla
Caveman Cave 1  
Frogmen Cave 3  
Hermit's Hut 1  
Mushroommen Cave 1  
Centaur Cave 2  
Magic Forest 2  
Ratmen Cave 3  
Ogre Cave 2  
Wormen Cave 4  
Medusa Cave 1  
Troll Cave 2  
Beholder Cave 1 Hidden in mountains north of Glomwon
Fort Glomwon town  
Dukhada town  
Icemen Cave 3  
Snowtroll Cave 1  
Anhsirk town  
Snakemen Cave 2  
Mermen Cave 2  
Dragon Cave 1 Hidden in north side of mountains to the northwest of Anhsirk
Insectmen Cave 2  
Ancient Temple 2  
Cannibal Camp 2  
Spider cave 5  
Tomb of the mutilated 4  
West Pyramid 3 A secret door leads to the Ascii level, but the level is currently bugged.
East Pyramid 3  
Tikku's Cave 1 On the island in the middle of the lake on the main continent.  Use Gate to get here.
Dark Castle 2 Shows up when you get the quest from Calma in Anhsirk.
Hell 9 From portal in Dark Castle
Secret Doors
Location Level Note
Goblin Cave 2 At dead end, leads to third level.
Goblin Cave 4 In the room in the back of the throne room.  Leads to Thoi.
Dwarven Temple 2 In room behind Ba'Dong
Kobold Cave 1 In the back of the throne room
Kobold Cave 1 In the north of the throne room
Kobold Cave 1 In sw corner of northern secret room off the throne room
Buglurgi 2 East side of southeastern room in inn
Orc Cave 1 Between pillars on north east side
Orc Cave 2 Southeast corner
Orc Cave 3 Southwest corner, in water
Abandoned Farm Basement South side of west room
Abandoned Farm Basement East side of south room
Witch's Hut 2 North at dead end
Slugmen Cave 1 To level 2 (north side of south room)
Slugmen Cave 2 East side of worm room with water
Slugmen Cave 2 To level 3 (east side of south room)
Slugmen Cave 3 West side of the west room
Slugmen Cave 3 2 secret doors in the north part of north room
Abandoned Castle 1 Southeast tower
Abandoned Castle Upstairs 2 secret doors between the storage room and the bedroom
Abandoned Castle Downstairs Southwest corner, after traps
Abandoned Castle Downstairs East wall right south of entrance to south section
Birdmen Cave 1 (west) North wall at right of entrance
Birdmen Cave 1 (west) North wall of first room on the right and then the north wall of the secret room
Birdmen Cave 1 (west) Southeast side of room to the east of Storage #2
Birdmen Cave 1 (east) North wall of northeast cell, and then south wall of the room at the end of the secret passage
Birdmen Cave 1 (east) North side of north "bedroom" in east corridor
Birdman Cave 1 (east) South side of one of the south bedrooms.
Birdmen Cave 1 (east) South west side of room in south corridor
Birdmen Cave 2 (south) In the back of the throne room
Birdmen Cave 2 (south) In the back of the secret room to secret part of level 1
Birdmen Cave 1 (secret) 4 secret doors in the entry room, one on each wall
Castle Galatako Town North side of east entrance, leads to catacombs
Castle Galatako Castle North side of Princess' library
Castle Galatako Castle East side of secret room off Princess' library
Castle Galatako Catacombs West side of north east alcove
Dwarven Mines 2 In King Haval's tomb
Frogmen Cave 3 End of west corridor
Frogmen Cave 3 East wall in south room off west corridor
Frogmen Cave 3 East wall of southeast room
Frogmen Cave 3 East wall of throne room (behind broken pillar)
Frogmen Cave 3 North side of throne room
Frogmen Cave 3 Southeast side of treasure room off throne room and 4 secret doors behind that.
Frogmen Cave 2 east side of southeast section of level
Frogmen Cave 2 North side of room in far east side of southeast section
Frogmen Cave 1 Southeast side on south wall
Centaur Cave 1 North central part, between the two rock outcroppings
Ogre Cave 2 West wall on east hallway (just southeast of water passages)
Ogre Cave 2 East wall just north of blocked hall
Ogre Cave 2 West wall of southwest side (just north of blocked hall)
Ogre Cave 2 West wall behind southwest secret door
Ogre Cave 2 West wall behind 2nd southwest secret door
Wormmen Cave 1 Southern wall of trapped hall in south of level.  Locked door leads to hall with a bunch of traps.
Wormmen Cave 2 East wall of northeast section of the cave
Troll Cave 2 Northwest corner of hall, go east then north from the entrance.  The secret is in the northwest corner of that hall.  And then north side of the secret room.
Anhsirk   Behind locked door
Snakemen Cave 2 Behind throne
Insectmen Cave 1 West side of south west "Egg" room ('K'ick the eggs to get through to the wall)
Insectmen Cave 1 Southwest corner of "Cocoon" room
Insectmen Cave 1 North wall of east corridor, just as it turns back west
Insectmen Cave 2 North wall of Queen's treasure room
Insectmen Cave 2 West wall of secret room off treasure room
Ancient Temple 1 North side of east central room
Ancient Temple 2 East side of secret area (entered from secret room on level 1) and then north side of that room
Spider Cave 1 North of entrance to second level
Spider Cave 2 North of entrance from first level
Spider Cave 2 North of entrance to third level and then north side of that hall
Spider Cave 2 North side of northeast room in south side of level and north side of that hall
Spider Cave 3 Lots of secret doors in entrance from secret area
Spider Cave 4 South side of southeast storage room entrance
Spider Cave 4 North side of room with mushroom and flowers
Spider Cave 5 North side of east room and then north side of that hall
Tomb of the Mutilated 1 North side of entrance (near blood spot)
Tomb of the Mutilated 1 East side of the secret room
Tomb of the Mutilated 2 West side of northwest tomb
Tomb of the Mutilated 2 North side of east room (with hammer smashed head)
Tomb of the Mutilated 2 North side of east secret room
Tomb of the Mutilated 3 West side of tomb with barb wire mummy
Tomb of the Mutilated 3 West side of west most tomb
Tomb of the Mutilated 3 South side of west secret room
Tomb of the Mutilated 3 North side of northwest storage room
Tomb of the Mutilated 3 West side of storage secret room
Tomb of the Mutilated 3 West side of second storage secret room
Tomb of the Mutilated 4 West side of cemetery
West Pyramid 1 North side of pyramid
West Pyramid 1 Lots of secret doors in entrance
West Pyramid 1 East side of southeast cell
West Pyramid 2 Southeast corner of southeast room
West Pyramid 2 East wall of secret room (goes to magic portal to Ascii level)
East Pyramid 1 West side of pyramid
East Pyramid 2 Northeast corner of one of the west rooms
East Pyramid 1 Southwest corner of west room, in east side of level
East Pyramid 3 Southwest corner of throne room
East Pyramid 3 South and east walls of treasure room
Tikku's Cave 1 East side of throne room
Dark Castle 1 East side of one of the prison cells
Quests
Quest Notes
Arena fighting By winning the arena fights in Odrewold and Castle Galatako you'll make a lot of gold.  Additionally, if you win everything you'll get a modified sword.  This does not show up in your quest log.

BUG: Sometimes an invisible guy shows up in the Castle Galatako's fights.  Attacking him causes the game to crash.  It appears this is a random problem.  I've gotten around it by not saving after every fight and if I hit it I reload.  However, if you save and the bugged fighter is the next fighter, you won't be able to complete the fights. 
Kill the goblin leader The mayor of Odrewold will reward you if you kill the goblin leader.  Go kill the goblin king and come back to him for a 1500 gold piece reward.
Find Thoi and take his to his brothers Thui, Thai and Thei have lost their brother, Thoi, Find him, and they will reward you.  (They are found in the North part of the first level of the Goblin Cave.)  Find Thoi in the secret room in the back of the Goblin King's throne room.  You can get either 1400 gold or a +1 ring of protection as a reward.
Find 5 lotus flowers for Loran Loran the potion dealer in southwest Odrewold will ask you for 5 Lotus flowers and will give you several good potions in exchange.  (This quest seems to show up after a few days, but I'm not sure when it does.  Keep coming back and eventually she will ask you.)
Kill Ba'Dong After you kill the Goblin leader, Vanril the guard captain in Odrewold will ask you to kill Ba'Dong in dwarven temple.  The reward is 2500 gold.
Find the Yellow Dagger A ranger on the second floor of the inn in Buglurgi will ask you to get the Yellow Dagger.  Go to the abandoned farm and get it from upstairs.  Give it to the ranger for 4000 gold and Mithril ring mail.
Kill the orcish chief The Mayor of Buglurji will ask you to kill the Orc Chief.  After wiping out the Orc Cave come back for your reward of Iron Plate Mail.  You also get several scrolls for accepting the quest.
Escort Charlene to her brother Charlene is in the basement of the Abandoned Farm. Take her to her brother in Buglurgi for 1000 gold.  You can get another 1000 by following the Baron upstairs and bribing him.  This quest doesn't actually show up in the quest log.
Witch's Quest Scotia lives in a cabin south of Buglurji.  She will ask you to get a item for her.  If you accept you'll be teleported to an area to get it.  This doesn't show up in the quest log and has no reward, but I thought it should go in here.

BUG: If you refuse the quest from Scotia you'll get into a state you can't exit and will have to shut down the game.
Search the ancient tomb near Cadar Yannick in Cadar will ask you to deal with a problem of his.  After clearing the ancient tomb come back and he will give you a mushroom that gives +2 Intelligence and +2 Wisdom.
Kill the mayor of Cadar On the road south of Cadar you'll run into a shady character that wants you to kill the mayor of Cadar.  He'll give you 4 very nice rings if you do.
Find Alisa's lost ring. Alisa is Ratchyr's maid in Gitala.  She'll ask you to fetch her ring from a bed in Turako's Inn, in Castle Galatako.  You get a very nice +2 Mithril Helm of Water Breathing in exchange.

BUG: Get this quest before finding her ring.  If you have the ring already drop it before talking to her.  If you have it in your inventory it may be removed and you won't be able to solve the quest.
Ratchyr asked you to eliminate the bandit camp near Gitala Ratchyr in Gitala wants you to take care of some bandits.  Clear the bandit camp and come get your 12000 gold.
Find out why the dwarves haven't delivered their monthly gold load to Castle Galatako Guanno, the mayor of Galatako, needs you to go talk to the dwaves.  After talking to the dwarven king come back for 3000 gold.
Examine the underground catacombs of Castle Galatako Herron, the high priest of Galatako, wants you to investigate the catacombs.  Once you kill the warlock in the catacombs claim your reward.  8000 gold and +2 Gnomish Boots of Tolerance.
Find out if there really is a phantom in the royal wine cellar Hidebor the royal counsellor wants you to investigate some rumors.  Kill the phantom in the wine cellar to get 5000 gold and a +2 Eternium dagger of mana.
Kill Scotia the witch The dwarven king wants you to get rid of Scotia (not that he really needs to prod you after that trick she played…).  You get 5000 gold and a +2 Dwarven huge hand axe in addition to your revenge.
Find the orb of the elven gods for Venla Venla, the magic book dealer, in Galatako will give you this quest after you finish the Dwarf quest. Get the orb from the Elven ruins.  She'll give you a book of shock ball, reality ripple, & self-teleportation + Elixir of Constitution for the trouble.
Escort Blostok out of swamp. Blostok is stranded in the southwest side of Frogmen swamp.  Escort him out of the swamp for 1200 gold.
Destroy the mushroom men Elgar the hermit, lives in a house west of Galatako.  He isn't able to gather mushrooms because they are fighting back.  Go kill the mushroom men to get several mushrooms in return.
Take Remu's gift to the mayor of Dukhada Remu, mayor of Glomwon, wants you to drop off a gift to the mayor of Dukhada.  Return to Remu for the payment of 4000 gold.
Destroy the icemen Galori, mayor of Dukhada, needs you to kill the icemen.  18000 gold awaits you if you complete the quest.
Destroy the cannibals The mayor of Anhsirk wants to expand, but some cannibals are in the way.  If you get rid of them he'll give you a cool 10000 gold + some other equipment.
Find the Idol of Ra Once you've taken care of the cannibals, Calma, the elder in Anhsirk, wants you to bring him the 'Idol of Ra'.  It is in the Pyramids.  When you bring it back to him he'll give you "The Devotee's Amulet".

NOTE:  You can sell the 'Idol of Ra'.  If you do, then you WILL NOT be able to finish the game.  Actually, you can if you know where the dark castle is.  Go to the square with the Dark Castle and press 'E' to enter it.  Even though it isn't shown you can enter. 
Retrieve the Divine Sceptre from Hell While this doesn't show up in the quest log, it is your final quest.  Calma will give it to you after you give him the 'Idol of Ra'.  Additionally, he will give you a Wand of create food and a Book of create food when you start the quest.
Other
1. In addition to the standard things to search (chests, shelves, urns, altars, etc) sometimes there are things elsewhere.  I have found two rings in beds.  Both in the Birdmen Cave.  One is in one of the bedrooms in the east corridor and the other is in a bed in the "High Priest's Quarters".
2.  Once you've finished the game once you'll be able to play the game with a single character.  This character starts with +15 to all attributes (based on the normal values).  I've played through with a Monk, so I know it is doable, but I'm not sure which classes it is doable with...