Nadi can be first encountered in the Moonrise Towers Prison, standing guard at the very end of the prison's walkable space.
Should the party attempt to help the gnomes and tieflings escape from the prison, Nadi can join The Warden in pursuit of the escapees should the cells be opened (either by the party, or by the Warden). Nadi can then engage the prisoners in combat and kill them if the party does not intervene.
Defending Moonrise Towers
If the Nightsong is freed and the Harpers launch their assault on Moonrise Towers, Bel is killed during the subsequent battle. His corpse is situated on the bridge leading into Moonrise Towers proper, surrounded by Holy Fire, at X: -154 Y: -113.