Hold [Alt] and type pwr or power at the magic screen. All wizards (including opponents) will be able to gain mana and cast all learnable spells, including the Spell Of Mastery.
Full map
Hold [Alt] and type rvl or reveal at the magic screen. Exit the magic screen, then re-enter the magic screen to enable the code. Note: This also affects opponents.
Microprose message
Hold [Alt] and type destin at the magic screen to display a message to send Microprose a copy of the saved game and a bug report. Alternately, click Left Mouse Button + Right Mouse Button at the magic screen.