­Omnath, Locus of Mana + Unslip the Soul

Ok, the somewhat iconic "Hey, gather all your mana; don't you go using it now..." creature and a limited worth Terror (by which, of course I mean technically better but costs so much that what's the point?)

So. Omnath is interesting because he rewards you for doing something you'd do anyway (draw mana) gives you a new thing you can't usually do (accumulate mana over turns) and then says "But hey, here's a good reason to not actually USE that mana".

Of course, that's also a bit eggs-in-one-basket-y.

I'm tempted to say that this mash results in Sengir Vampire. It's a creature that grows bigger when you do stuff you'd do anyway (kill creatures, instead of draw mana) and is iconic - but it's overpriced, just like modern kill spells.

Still, there's something there. How about a creature that grows bigger whenever anything dies (and that, right there, would be a perfect fix for a modern Sengir) but somehow makes you not want to use that - forbid the graveyard maybe? That's a somewhat rarely used resource though. Combat is a MUCH more frequent resource.

Ok; so it grows as stuff dies - and then shrinks.. when you initiate combat? Too overly limited; Omnah does at least give you one shot to use the accumulated mana. After combat? An opponent could just do a sacrificial weenie attack to wipe out all your buffs. So, after your attack.

Seems workable. Ok; shorter wording gives me a couple of tricks you can look for - he recovers from bad counters too; you can give him vigilance or untap him. I don't see that as a problem; a single big creature is a threat but not an insurmountable one; and that much effort should be rewarded.

Make it a 4/4 flyer in homage to my initial idea; and since it's a named creature we'll go legendary, which means mythic.

A creature that drew cards, or that had a kill-stick ability would be more useful, but not every card is a 'run 4 of'.

Cost... Sengir is my starting point. But... oh sod it, this is mythic land, mythics are broken with a capital "Balance". (Not Balance) Make it a square cost, so that ti actually sees play. Nothing worse that "Wow! I got a one in a thousand card! ... it sucks! I can't imagine putting it into my deck!"