NPCs composing that spawngroup :

a_bile_golem (100%)

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

charasis_125, range=90 (-64,476,22)

a_bottomless_feaster (50%)
greater_war_boned_skeleton (50%)

charasis_127, range=29 (-170,532,14)

charasis_129, range=31 (-116,532,14)

charasis_130, range=70 (-208,549,22)

an_undead_oblation (50%)
greater_war_boned_skeleton (50%)

charasis_133, range=89 (-156,429,22)

charasis_134, range=89 (-132,429,22)

charasis_143, range=94 (-144,423,22)

a_sepulcher_skeleton (100%)

charasis_208, range=34 (-127,548,4)

greater_war_boned_skeleton (100%)