mtg commander hydra deck Zaxara, the Exemplary Tribal X-Spells Magic – CommanderComplete Whenever Kalonian Hydra attacks Thousand Maws- A Temur Hydras

With its upshift in rarity and two genuine printings, Cavern of Souls is a very expensive card

What did those pieces of cardboard say again

Historically, the Reserved List cards (like Dual Lands and the Power Nine) hold value best

(Activate each exhaust ability only once.) You may activate this creature's exhaust ability without discarding cards if you just want to put a +1/+1 counter on it

Go to that combat phase and you either get the red Overrun for a great reason to attack with everything, a new hand of options, or you can pick off one of the more annoying blockers or send a Lava Axe to the face and completely change combat math

I think you have to have enough draw to warrant this seeing play in a typical Eldrazi deck, but if you're going hard into the blue/control shell it's a nice way to get to your fatties faster