Windsor Castle

At the end of each of your turn, if Windsor
Castle was not tapped, put an Abandon
counter on Windsor Castle.
{t} Add {1} to your mana pool. Remove all
Abandon counters on Windsor Castle.
If there are Abandon counters more than the
number of players in game, Windsor Castle
and target creature, planeswalker, or artifact you control gains Hexproof. Targets may only
be changed if you lost and regained this ability.