The official GemStone IV encyclopedia.
The emaciated hierophant stands short for a human, and might pass for one except for the storm grey eyes that swirl with unearthly energy. Long robes that appear to float in the air gap to reveal an ornate tunic and breeches with polished green leather boots to the knee. A long golden chain hangs about his neck, a small glowing red crystal suspended as a pendant there. Intricate tattoos cover his flesh, drawing ornate and unrecognizable patterns that glow a dull red and seem to pulse along as if it were blood.
Hierophants, though ranger-style semis, are highly susceptible to Dark Catalyst (719). This spell is normally only moderately effective against semis.
Hierophants will not walk around or spawn with spells prepared. However, they may, on some occasions, cast Spirit Strike (117) on themselves with no target in the room.
Hierophants can be stunned easily but will also break stuns during their next action window. This will slow them down and allow you to stun them again in order to prevent their most dangerous weapon: spikethorn. They are rather squishy as well.
Hierophants are able to break through stuns and Web (118).