There are a lot of things that need to be unlocked in DD.
For all unlocks that involve finding something in a dungeon run, you are required to leave the dungeon alive. You do not have to win, and the item will not be unlocked if you die.
Human: unlocked by default
Orc: Search Western Dungeons for sub dungeon with Orc who will have you drink a potion.(Note Western Jungle seems to ALWAYS give Taurog sub dungeon until completed, so Druid's Grove may be ideal if you do not want to unlock Taurog).
Goblin: Search Southern Dungeons for a sub dungeon with a Goblin who wants money.(Note Southern Swamp seems to ALWAYS give Tikki Tooki sub dungeon until completed, so Hexx Ruins may be ideal if you do not want to unlock Tikki Tooki).
Fighter: Guild lvl 1
Berserker: Guild lvl 2
Warlord: Guild lvl 3
Wizard: Mage Tower lvl 1
Sorcerer: Mage Tower lvl 2
Bloodmage: Mage Tower lvl 3
Priest: Church lvl 1
Monk: Church lvl 2
Paladin: Church lvl 3
Thief: Thieves' Den lvl 1
Rogue: Thieves' Den lvl 2
Assassin: Thieves' Den lvl 3
Goat: not yet added
Gaan'talet(Hard): Opened by quest progression in game and getting one of every trophy.
Bazaar lvl 1: Buy Portal scroll and exit the level without dying.
Bazaar lvl 2:
Bank lvl 1: Tutorial
Bank lvl 2:
Witch lvl 1: Eastern Tundra subdungeon. You have to gather 5 items from killing plants
Witch lvl 2:
Alchemist lvl 1: Buy Philospher's stone and exit the level without dying.
Alchemist lvl 2:
Explorer's Guild: Tutorial
Guild lvl 1: Tutorial
Guild lvl 2:
Guild lvl 3: 2,000 gold, requires Guild lvl 2
Mage Tower lvl 1:
Mage Tower lvl 2:
Mage Tower lvl 3: 2,000 gold, requires Mage Tower lvl 2
Church lvl 1:
Church lvl 2:
Church lvl 3: 2,000 gold, requires Church lvl 2
Thieves' Den lvl 1:
Thieves' Den lvl 2:
Thieves' Den lvl 3: 2,000 gold, requires Thieves' Den lvl 2
Shop Scroll: Bazaar lvl 2
Apothecary: Bazaar lvl 2
Black Market: Thieves' Den lvl 2
Bet on the Boss: Thieves' Den lvl 2
Smuggler Den: Thieves' Den lvl 3
Patches the Teddy: Thieves' Den lvl 3
3-Slot Locker: Guild lvl 2
6-Slot Locker: Guild lvl 3
Magnet Fire: Mage Tower lvl 2
Extra Glyphs: Mage Tower lvl 2
Fewer Glyphs: Mage Tower lvl 2
Extra Boosters: Mage Tower lvl 3
Guaranteed God: Church lvl 2
Extra Altar: Church lvl 3 (requires all 9 gods)
Expanded Potion Kit: Witch
Sword: Blacksmith lvl 1
Shield: Blacksmith lvl 1
Bear Mace: Blacksmith lvl 2
Perseverance Badge: Blacksmith lvl 2
Slayer's Wand: Blacksmith lvl 2
Really Big Sword: Blacksmith lvl 3
Compression Seal: Alchemist lvl 1
Transmutation Seal: Alchemist lvl 1
Translocation Seal: Alchemist lvl 2
Crystal Ball: From completing quest to win Den of Danger with second tier classes.