Shard Hoarder

When Shard Hoarder enters the battlefield target opponent reveals their hand, you choose a
nonland card from among them, that player
exiles that card.
For as long as that card is exiled Shard Hoarder
gets +1/+1 equal to the converted mana cost of
the exiled card.
When Shard Hoarder leaves the battlefield return the exiled card to its owner's hand.
Not many of them care about physical things.