Letty Whiterock, Snowmistress

When Letty Whiterock enters the battlefield, set your season to Winter.
(All lands you control now produce only blue snow mana and lose all other text.)
{t}: Add {u} for each creature with a stun counter. Do this as long as your Season is Winter

Pay {s}: Put a stun counter on any creature. This cost increases by one {s} for each time it
has been activated this turn.