This is what the group faced during the Conjurer's Challenge. Bear in mind they were 17th (now 18th level), and did not have all their powers intact.
Like all daemons, there are those who manage to climb higher in the chaotic ecology of the pit than their mundane ilk. This monster is a normal Zovvut who's terrible cruelty and blasphemous strength has elevated it above the rank and file of its kind.
It is a hateful engine of endless destruction, and only the very powerful or foolish would attempt to conjure it and risk it escaping their control.
(Click to enlarge with rage)
Zovvuts are official D&D demons, found in 3.5 and 4e. Naturally, that means they are copyrite Wizards of the Coast (though this variant is my own creation). As always, you need to add half the monsters level to the modifiers by the statistics to make them accurate, and this stat block was created with THIS.