The Legion of Super Skulls (Vigilante; ID 27660)

[Heraclea]

One big map mission on this.  This is another tanking skill drill.  The object here is not so much to survive the mobs as it is to keep your NPC allies and escorts alive.  They can be rather flighty and suicidal, and are wont to run away and get in over their heads.  They have no damage dealing attacks. 

 

Normal mode is with Archvillains ON.  There are no Archvillain class enemies in the mission; what having AVs on does is to allow the NPC allies and escorts to spawn as archvillains, making them a bit more durable (though hardly immortal).  Challenge mode is with Archvillains OFF.  This makes the friendly NPCs spawn as only elite bosses, which are a lot less tough and much harder to shepherd through to the end.