Carth the Lion is a rare Legendary Creature — Human Warrior card from Magic Online Promos (PRM), collector number 91345.
Whenever Carth enters or a planeswalker you control dies, look at the top seven cards of your library. You may reveal a planeswalker card from among them and put it into your hand. Put the rest on the bottom of your library in a random order. Planeswalkers' loyalty abilities you activate cost an additional [+1] to activate.