I like the concept of the card a lot, the elephant defrosting and running amok is great, however I don't like the card itself.
The mammoth won't come into play until late into the game and you have to worry about surviving that long. the high cost means you can't spam them and watch them defrost one after another.
In the current game, you have 2 options. Quintessence and parallel universe. I don't think quint is SUPPOSED to remove frozen status and if it is supposed to, I don't think it should. If it continues to tho, the combo may be broken. If the combo is changed, you're left with PU, which would result in the basic aether stall/beatdown deck.exce[t slower due to dual elements and frozen status. Might as well stick to mono aether since it has fewer weaknesses.
The trample does fit a mammoth, but I agree that it feels a bit tacked on to this card. Besides, earth has not really been a creature control type of element.
I also wouldn't be surprised to see anti-freeze cards or time cards similar to adrenaline (honestly I expected a time version of adrenaline before adrenaline) which may break the card by removing one of it's limiters.