The Buyer will have a dispute opened against them with Invaluable
He also provides a huge array of abilities, although its interesting that the un-melded version wants you to go creature-wide while the melded version is arguably better suited for a board of larger creatures or a controlling strategy by forcing lots of discards
it just never ends
So OP10-018-ten-layer-igloo is an answer for a high-power attack, or it could be used to shut down two attackers, countering the first with the Power boost and reducing the Power of the other attacker before it gets to attack
One of the best phasing cards in Magic, Teferi's Protection is like a mega-fog, protecting you and your permanents not only from combat damage, but from board wipes, removal, and other damage sources, too
Her end-step return ability from the graveyard means any Elf you mill or sacrifice comes straight back to play keeping your graveyard toolkit stocked