Last arena I went into I got offered the new orc Summoner as a rare. I had been meaning to try him out so I grabbed him instead of some otherwise possibly better direct damage choices. The game decided to reward me and then threw in Treant, Black Beast and Bladedancer as Ultra-Rares. Black Beast + Summoner? I really wanted to try that. And the arena was just waving it in my face 
The team
In action:
It is probably far from an ideal arena choice. It is rather slow going, though the Soul Blade offered some very nice direct damage while waiting for skulls.
And while other setups may let you race through the fights at breackneck speed, this was actually a lot of fun. The challenge was keeping the black beast alive early on. Once it had eaten the goblin and started munching on ghouls, nothing could stop it. And if a ghoul managed to use its own power before getting munched on, so much the better.