They drop the new Sunder charms. Very rare.. if you want to make it worth your time do it on Players 8 and TZ Acts 1-5. Hit all the S and A tier spots. Every one you kill they go up in a rank. 4+ have an added loot table. 5 is the max! New games reset progress
I've just done 2h of terrorized acts, I find it tiring like a chore! Not great
