The Watcher

Flying, Shroud
{1}{u}{u}{t}Counter target spell or ability.
{2}{b}{b}The Watcher becomes indestructible until
end of turn
{5}{u}{b}The Watcher becomes an enchantment,
attach Watcher to an opponent's creature,
whenever enchanted creature attacks its controller
loses 3 life discards 3 cards, or mills 3 cards.