Thanos, Mad Titan

This card gains +1/+1 for every Infinity Stone attached to it.
When this card enters the battlefield, you may
return target Infinity Stone from the graveyard or
exile zone to the top of your deck. If you do, sacrifice 2 life.
{t} Add {s} to your mana pool.
When this card has six Infinity Stones attached to
it, transform it.