The buff that is granted to the named for each scorpion near is called "Stinging Empowerment".
He cannot seem to have more than 2 of these up at one time.
It does the following:
INT & STR +170
Base Auto Attack Multiplier +1,000
Multi Attack Chance + 30
Attack Speed + 50
On a hit 20% Chance to cast 1000 Stings on target of attack, Lasts 5 seconds
3 times Heat damage in AOE and every 5 seconds
Dazes Target
Reduces Healing Received by 25%
The power drain is caused by the Noxious AOE "Stinging Torrent" but it does very little damage.
As a note, the Adds are not big damage, but for each one near the main named he gains a power drain that will suck up a lot of power if they are not pulled away or burned down.