ToME Wiki
Quests
A personal opinion: quests rock. Whilst the random generation of dungeons is a mighty fine thing, and indeed it wouldn't be a roguelike without it, the recreation of specific goals and situations adds a sense of purpose and pride for players. The risks and rewards should be massive.
The Retreat of Osgiliath
"The hordes of Morgoth assault Minas Tirith! You must slow their advance or we are lost"
A ruined version of the Theme city forms the basis of this quest. You will be given a doughty force of Gondorian warriors and a few Knights of the Swan to hold up against the massive onslaught.
A script will be inserted to ensure that the city will never be free of orcs (will auto-generate 10-15 new Uruk every 50 turns), but the initial group will also have several Orc Uniques, Trolls, undead and Gothmog, Lieutenant of Morgul, a fell warrior. The job is to "hold" Osgiliath (not retreat) for 5000 turns. Apart from the existing monsters, and the new boatload of Uruk warriors every 50 turns, the Witch-King of Angmar appears at the 4800 mark, along with his Winged Horror escort. Probably not a good idea to confront him, though if you're REALLY game you may prevail. The city will be scattered and broken and a straight-up battle will not occur, so things should get highly messy.
The reward will be the Palantir of Osgiliath. See Items for the new effect of Palantiri... 
The Paths of the Dead
"We are lost without aid! You must risk the Paths of the Dead to gain the aid of the Oathbreakers!"
This quest has three parts. First is the finding of the Black Banner, which would be during normal gameplay (for the Black Banner's effects, see the equivalent Theme artifact, minus pretty much everything except Undead ESP). Upon finding it, you get a "go see Aragorn" message. Upon reaching Minas Tirith, he tells you to go deep into the paths of the dead to find the oathbreakers. They are found (predictably) at the very bottom of the Paths of the Dead. Feagwath is still down there, and when you kill him you get:
"As Feagwath fades from existence, hordes of Undead Warriors surround you. Their leader approaches 'Now that we have been released from the bondage of that evil sorcerer, we will fulfil our oath to the King of Gondor.'"
And you've completed the quest. Go back to Aragorn and he will upgrade your Banner to the full Theme version, with Summon Undead, Invisibility and "the works".
"Their Oath shall be fulfilled! The strength of the undead may be enough to tip the balance. Unfurl your banner in the name of Minas Tirith! "
Astute reader may have noticed that this is almost a re-run of Narsil. But what of it?