Smaug the Terrible

Flying, Trample
When Smaug the Terrible enters the battlefield,
create a legendary artifact token called the
Arkenstone with "At the beginning of your end
step, create {x} treasure tokens, where {x} is the
amount of life you lost this turn".
Whenever a creature you control destroys another
creature, you may have you and target opponent
each lose 1 life.