Always back up your game before attempting these type of cheats
In Ultima 8 there is a debuging code that allows you to manipulate the game. The way you're supposed to do this is to use some sort of debuging program, I simply just used 'debug' in DOS.
In the :\ulitima8\gamedat directory make a file called 'avatar.deb'
in this file type
and save the file.
Debug avatar.dat < avatar.deb which should look like this
:\ulitma8\gamedat\debug avatar.dat < avatar.deb
As soon as you load the game save it, (you will be prompted to put your name in at the start so it's a good idea to do this when you're just about to start)
in the game press ctrl and F1 and a list of what you can do will come up
eg. shift F5 or F4 will give you all the weapons and armour or something ( note they will be on the ground around you so you'll have to pick them up)
the F7 key is a key factor to the cheat codes, it can move you to any location providing you can input the exact locations which involves x,y,z and map numbers. You can also move to any NPC, which are the actors in the game such as Devon or Rhian etc.
The best thing that could ever be done for this cheat would be under the first column. It's name is Hackmover. By enabling this you can move anything from anywhere, you can pick up anything from any where permitting it is in the same screen as you. You can move locked doors out the way, move ghouls away from you, you can even move yourself into a room or anywhere with the mouse cursor. There are limitless things to be done. But try not to move the floor, which happens, it is really a pain, because you can never move it back to the same exact place. But with moving normal objects it helps you.
One more thing is that you can click on yourself once and a whole list of more cheats come up such as
Demos= that allows you to do some parts of the game which are not controlled by yourself
Spells= this gives you the ability to use all the spells of all the titans (except tempestry, because you can't get that in the game anyway normally)and without the use of reagents or books or nothing just click on it and enjoy
Information= when you click on this, a cross hair will come up, click on the ground and it will give you x,y,z, and map numbers (and more)this can be used with the F7 command for reference or for easier movement within the game.
There rest are there for you to find out about yourselves, I had to when i first used it. Hope it helps