Percy Jackson, Son of the Sea

As long as you control an Island, Percy Jackson
has islandwalk.
As long as you control three or more Islands,
Percy Jackson has hexproof and "If a source
would deal damage to Percy Jackson, prevent all
but 1 of that damage."
As long as you control seven or more Islands, sea creatures you control get +1/+1 and have
hexproof.
As long as you control twelve or more Islands,
you control all sea creatures.