Cheat mode
Note: This cheat involves modifying a game file make a backup copy of the file before going on. By enabling cheat mode can also make it hopeless to finish the game as it is suppose to be. Then use a text editor to change the "default.kmp" file in the game directory. Add the lines below to the "[Cheat Commands]" heading:

alt+shift+a = toggle_avatar_invulnerable
alt+shift+b = pass_one_hour
alt+shift+c = unpass_one_hour
alt+shift+d = sunrise_sunset
alt+shift+e = pass_one_minute
alt+shift+f = unpass_one_minute
alt+shift+g = toggle_sun
alt+shift+h = toggle_wind
alt+shift+i = toggle_storms
alt+shift+j = toggle_avatar_fast
alt+shift+k = toggle_avatar_fly

Then, press one of the keys below while playing to activate the desired cheat.

Note: By you enabling the cheats it can cause parts of the game to hang up, like when you fly over a trigger spot earlier than normal.

Additional codes
The codes below need v1.07 of the game, and can be bound to any key combination in the "default.kmp" file as described earlier.

recharge_mana
fill_spellbook
spells_0-2
spells_3-5
spells_6-8

Kill Lord British
When you begin, go to the refrigerator locate the rat poison, then use the breadmaker. When you reach Britain, go to his secret dining room. Then replace the bread with the poison bread. Lord British will eat it and die. Note: Save before you do this since the guards will also kill you.

Hidden teleporters
Find the fence with no gate behind the Avatar's house. Then climb on the training dummy and jump over the fence. Locate the level that is hidden close to a bush by the large tree. Now pll the lever to find teleporters that will equip your character with armor and allow you to travel to different places in Britannia. Note: You can not go back by teleporter once you do leave.

Invisible to monsters
Just press B to open your backpack and then attack monsters. They will ignore you as long as the backpack stays open. Note: Drag the backpack to the edge of the screen to get a better view.