Spear of the Usurper

Equip {3}
Equipped creature gets +2/+0 and has First
Strike and "Whenever this creature deals combat damage to another creature, you may gain control
of that creature if you don't control another
creature you don't own."
"A prince's body double used this spear to slay his liege,
and met his own fate on the same edge."
-Weapon Data