Thorin, Cursed of Erebor

Whenever Thorin, Cursed of Erebor enters the battlefield, you become the monarch. Then
create a colorless legendary artifact token called
Arkenstone with shroud, indestructible and
Creatures that attack you get +2/+2. Whenever a
player becomes the monarch, they gain control
of the Arkenstone.
As long as you control the Arkenstone, creatures
you control gain first strike and vigilance.