Same as a nightmare, just different graphics. You could heal one with 4/6 chiv , but will still die against bosses. Cant rezz it without vet/lore skill or npc vet.
More of a pvp thing i believe, since you can have 2 of them.
Could also be paired with a fire beetle or a lowland boura .Quite nice for 4x bard i believe, but nothing imba.