Druid of the North

Cumulative upkeep-Add {s} for each age counter.
(At the beginning of your upkeep, put an age counter
on this permanent, then sacrifice it unless you pay its
upkeep cost for each age counter on it.)
Whenever a snow land enters the battlefield
under your control you may pay {s}. If you do,
create a 1/1 white bird snow creature token with
flying.