For the retail version:

 Activate the chat mode and type

 iamgod             - God mode
 iamgoddess         - God Mode in the last stage
 smoghead           - Healing
 debug on           - Debug mode ON
 all weapons        - activates in debug mode a list of objects
 give (weapon name) - Get (weapon name)
 gimme (item name)  - Get (item name), see below
 debug off          - Debug mode OFF
 fly                - Toggle flight mode
 drop               - Land with flight mode active
 switch             - Switch view to nearest enemy
 foghack            - No fog
 opensezme          - Unlock doors
 speed (1-50)       - Set game speed
 fov (6-93)         - Change speed
 giants             - Kill nearby enemies

 Item List

 Use any of the following with gimme code. Some items can only be obtained
 on the levels they normally appear on:

 health elixir
 potion of life
 great sword
 battle axe
 battle hammer
 altir's mace
 sword of flame
 ice hammer
 sword of ice
 lightning axe
 long sword
 mace
 mithril great sword
 mithril axe
 boomerang
 fire boomerang
 mithril hammer
 mithril long sword
 mithril mace
 magic scimitar
 magic short sword
 scimitar
 short sword
 speed scimitarv mourn bringer
 potion of invisibility
 potion of invulnerability
 flaming sword
 long bow
 arrows
 lightning crystal
 fire crystal
 ice crystal
 leather
 plate mail
 banded mail
 dragon armor
 rift crystal
 runeblade
 bell hammer of alwarren
 rune cage key
 scale mail
 chain mail
 tunnel entrance key
 crusher room key
 house key
 studded leather
 storage rune
 elemental amulet
 flaming arrows
 poison arrows
 explosive arrows
 energy bow
 energy arrow quiver
 energy bow key
 goblin access key
 mithril throwing axe
 ice arrows
 mithril throwing hammer
 jail key
 dark scimitar
 magic arrows
 potion of invulnerability bronze
 potion of invulnerability gold
 potion of invulnerability dark
 heavy bow
 speed bow
 heron's crystal
 tuiri's soul crystal
 dragon armor rune
 lava rune
 succubus mirror
 mystic key
 atimar's blade
 dead man's key
 rune of stone
 grungle's hammer

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 For the demo version:

 Go into chat modus and type in the following codes:

 sanctuary  - Invulnerability
 debug on   - Debug information
 debug off  - Hrrrm
 smeghead   - Reload energy