The codes can be entered at any time in-game. Here’s the full list of codes:

"I have every thing"
ihet = weapons, ammo, 1 upgrade point, 1 stats point, refills health and mana pools

"I have the key"
ihtk = keys

"I have all the spells"
ihats = all the spells

gotoeXmYY = teleports the player to a set level, where X stands for the episode (where X is a number from 1-5), and where YY stands for the map number (where YY can be any number between 01-12, with level five going up to 11 only)