This also counters most red instants and sorceries, the odd one from other colours too
He does not like you at all, and if you play any sort of a spell, you are about to take some serious hurt
You could combine it with cards like Bristlebane Battler to make more saprolings (or even better, to leech from an opponent that has that card and kill it later by doubling its counters)
These options get sunny checkmarks and those ever-popular smiley faces you see used in text messages
This works with all permanent types, and means that if you sacrifice a treasure token, you not only get the mana from the token itself, but Korvold gets stronger - and you draw a card, too
TYPE Instant Arcane ABILITY You may put a creature card from your hand onto the battlefield