Undercurrent Eidolon

Bestow {2}{u} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Skulk (This creature can't be blocked by creatures with greater power.)
Enchanted creature gets -2/+2 and has skulk.
A soul born of the Siren Sea.