Grak, King of the Bog

Whenever Grak enters the battlefield or attacks, you may exile a card from your graveyard. If you do, create a number of 1/1 blue Frog creature tokens equal to the exiled card's mana value.
{1}, Discard a card: Choose one —
• Target creature an opponent controls loses all abilities and is a blue Frog creature with base power and toughness 1/1.
• Draw a card, then discard a card.