These use a default basic melee attack with okay damage.
They have a Leap Slam skill listed, but they don't seem to use it at all.
They use a Lightning Storm with decent base damage, it has a 4 seconds cooldown and lasts for 3 seconds. It has one impact every 0.15 seconds.
These have 40% the life of a Primal Crushclaw.
They have innate 75% cold resistance.
Overall,
Cool Lightning storm ability, can do quite decent damage if all of the lightning strikes hit the target.
These can be found in T17 maps randomly, or the node Invasive Adversaries can be allocated on the atlas skill tree(Top side, just to the right of the Maven keystone).
This video was recorded in patch 3.24.