Display the key prompt during game play, then type doomsday to enable cheat mode. Then, display the key prompt again and activate the following cheats by entering the corresponding codes:

CHEAT FUNCTION - CHEAT CODE
Toggle easy kills - onekill <on or off>
Toggle invincibility - invulnerable <on or off>
Additional Hit Power - hit 999
Additional Intelligence - int 999
Additional Money - money 999
Additional Strength - str 999
Additional Dexterity - dex 999