Hilltop Grove Sentry

Flying
Hilltop Grove Sentry enters the battlefield with
four +1/+1 counters on it. At the beginning of
your upkeep, you may remove any number of
counters from Hilltop Grove Sentry. If you do,
add {1} to your mana pool for every counter
removed this way.
Whenever you cast a Forest, put a +1/+1 counter
on Hilltop Grove Sentry.