NPCs composing that spawngroup :

a_crag_sentinel (20%)

a_rock_sentinel (14%)

a_stone_sentinel (66%)

NPCs spawning around that spawngroup :
(Max range : 100)

thundercrest_monocle_180, range=37 (2384,1935,-46)

a_slag_sentinel (100%)

thundercrest_monocle_358, range=97 (2390,1870,-52)

Messenger_Drake (100%)

thundercrest_monocle_14_3, range=0 (2358,1962,-46)

a_rock_sentinel (100%)

thundercrest_288053, range=37 (2384,1935,-46)