Koriga, Deepwater Mystic

Hexproof.
Koriga, Deepwater Mystic can't be blocked.
Whenever a creature you control escapes if it's
green or blue it gains your choice of hexproof
or it can't be blocked and is a merfolk in
addition to its other types for as long as Koriga
is on the battlefield.
Escape—{1}{g}{u} Exile 4 other cards from your
graveyard. ( You can cast this spell from your
graveyard for its escape cost.)