cards in foundations mtg Magic the Gathering® Play Booster Card Pack, 1 ct Battle your friends with powerful creatures and spectacular spells in Commander MTG FOUNDATIONS - Complete MTG

You might also run into this creature in the 99 of decks led by commanders like The Gitrog Monster and Oskar, Rubbish Reclaimer

They are featured in the Amber Sing Together card, which is a mechanic that was introduced in set four

And second, it's a two-for-one

(If this creature isn't monstrous, put ten +1/+1 counters on it and it becomes monstrous.) When Grim Giganotosaurus becomes monstrous, destroy all artifacts and creatures other than Grim Giganotosaurus

This means that theyll be able to cast the first spell they reveal on top of their library with mana value less than or equal to that of the card that they shuffled into their library