During the Daedric quest "Waking Nightmare", troll fat may be found under a side table in one of the other rooms of Nightcaller Temple.
A third sample can be found inside a secret room if one opens a wardrobe downstairs.
The Dragonborn can also find some troll fat if they own Hjerim, in Windhelm.
Some troll fat can be stolen from the shed with the Alchemy Lab to the right of Malacath's Shrine.
Atub asks for Troll Fat and a Daedra Heart to use as an offering to Malacath, the patron Daedra of the Orsimer, in hopes that he might respond to the wise woman's prayers and guide the tribe in their time of need. The giants have taken advantage of this, assailing the stronghold regularly, as well as overtaking the shrine of the Daedric Prince Malacath. Chief Yamarz, the tribe's chief, has become weak and cursed. With the general exception of other Orcs, Orc tribes will initially be mistrustful of outsiders. If the quest to find The Forgemaster's Fingers has been completed, the gates are already unlocked. The Orcs will unlock the doors and come out to fight any wild animals, such as bears, that attack near the gates. If a fine is paid at this point, entrance to the stronghold will be gained. Steal any of the equipment from Ugor that is laying on the ground, thus causing the accusation of stealing, whereby the Orcs will unlock the door and come out of the stronghold. Upon talking to Atub, the gate will unlock. The stronghold may still be accessed by climbing the mountainside bordering the far left side of the entrance. If it is not possible to save Ugor, one of the following tactics will allow access to the stronghold: However, if she is rescued, the quest will be much easier depending on how quickly the giant is slain. If Ugor, one of the orcs fighting the giant, dies when entering the stronghold, then starting the quest will be more difficult. As the stronghold is approached, the tribe of orcs will be engaged in battle with a giant. Largashbur is an Orcish stronghold found near the Jerall Mountains in the south of The Rift region.
Place Shagrol's Warhammer on the Shrine in Largashbur.
Take Shagrol's Warhammer back to Largashbur.
Bring Troll Fat and a Daedra Heart to Atub.
Find out what's happening in Largashbur.
Atub, the wise woman of the tribe, has asked me to find her a bowl of Troll Fat and a Daedra Heart so that she may contact the Daedric Lord Malacath for guidance. The orcs of Largashbur have been constantly besieged by giants, and are forbidden to leave their stronghold.