In best-of-one, your sideboard size gets reduced to seven cards
The Most Impactful Cards of Magic: The Gathering Adventures in the Forgotten Realms Worlds collide as Dungeon & Dragons meshes with Magic: The Gathering, to create an all-new card set with the lore and enchantment of both universes
Obvious use in Sami, Wildcap Captain aside, there are plenty of decks from Osgir to Daretti that want cheap equipment in play to weld away or to recur from the yard
For seven, it clears every nonland permanent your opponents control
BPhillipYork: Well, there's probably something abusive you can do by untapping but other than that specific combo it's pretty meaningless
In any vampire deck, a turn 1 Blade of the Bloodchief spells doom for your opponents, and there are a couple infinites you can pull off with the Blade's counter production