Reclusive warlock

Seclude (at the beginning of your upkeep you may
exile this creature under an island or return this
creature from exile if it is secluded. If this creature is
the only creature exiled under an island it is
"secluded." Other players cannot activate this ability).
Whenever you cast an instant or sorcery spell
create a 1/1 blue spirit creature token.
{2}{u}: exile this creature under an island.