Caliburn, Slayer of Kings

Soulbound.
Caliburn Equips to whichever creature he is soulbound to, Caliburn can only bind to a creature with a different name to his previous target if he has left the battlefield since.

Equipped Creature Has First Strike and "when this creature attacks choose one:".
•Untap this creature and gain +0/+5 until end of turn.
•Gain +4/+0 and Trample until end of turn.
•Create A Treasure Token.
{bull}Transform Caliburn if you control 3 other Legendary Artifacts and a creature with Haste