Heimdall, the Protector

Indestructible
As long as your devotion to white and blue is less
than seven, Heimdall isn't a creature.
As long as Heimdall is untapped, creatures cannot attack you or a planeswalker you control unless
their controller pays 2 for each attacking creature.
{x}{u}{u}{u}, {t}, Creatures cannot attack this turn
unless their controller pays {x} for each attacking
creature.