Originally posted by Yakumo_2020:

I've never found a surtling core in a Troll cave.

Only the Crypts and Buirial Chambers in the Forest.

Other source would be a spawner in the swamp but unless your geared for it do't even try.

Also a small tip. The Troll hide armor has the same armor values as bronze armor but is easier and cheaper to upgrade so save your metal for crafting stations and upgrades and a couple Karves.

Good luck