Advanced Dungeon's and Dragon's: Pool of Radiance
Sent in by Peter Tosco
After defeating Tyranthraxus, you are congratulated and the credits roll
while the screen shows pictures of the main characters. Then you may
return to city hall where the clerk will give you your reward. She'll also
give you a character sheet, a password 3+ pages long that allows you
transfer characters to other games (I never figured out how to use it).
The clerk also says you "may kill the remaining monsters if you wish."
In other words, there's probably no true ending to the game, but you
can still discover many of the secrets you may not have found before
you killed Tyranthaxus.