Wartortle

Mutate {u}{u},
{u}{u}{t}: This creature fights target creatures
equal to the number of times its mutated.
While this creature is tapped reduce damage it
takes by half, rounded down. When you reduce 2
or more damage this way you may cast Blastoise,
for its mutate cost, targeting Wartortle, from
your hand, graveyard or library.
"It is a well-established symbol of longevity."