A Troll Head Trophy - NWN Side Quest (Chapter 2)

A Troll Head Trophy is a side quest that begins by speaking with Lenton inside of the Archaeologist Barracks on the East Road map. To gain access to these barracks you'll want to accept East Road: What Lurks Below from Jax who is standing outside of them. You'll find Lenton in the back of the building occasionally attacking a combat dummy. Wait patiently until he is done attacking and you'll be able to speak with him.

For this quest you'll be tasked with entering the Troll Caves and defeating the Troll Chieftain who is on the 1st floor. You can find him in the northern portion of the zone behind a locked door, use my screenshot below if you need help locating him. Defeat him and loot the Head of the Troll Chieftain from his corpse, this will be our proof of kill for Lenton.

You'll also find a Corpse on this map which has the Journal of Synth La'neral on it. This item is used in Linu's Tale which is a Henchman Chapter 2 quest involving Linu, the Cleric Henchman. One other thing to note is the nearby exit will lead you straight to Janis for The Simpleton's Mother side quest. You're likely going to be doing both of these quests at the same time.

Return to Lenton inside of the Archaeologist Barracks and give him the Head of the Troll Chieftain to complete the quest and get your reward.