Blade of Selves is an Equipment that features the Myriad mechanic, new to Commander 2015. While the effect of Myriad is useless in one-on-one Magic, in multiplayer Commander games, this Blade can be extremely powerful if equipped to the right creature. This Blade gives the equipped creature Myriad, which means for each player beyond the creature the equipped creature is attacking, you make a token copy of that creature which is tapped and attacking each other player (or a planeswalker that player controls). This seems all well and good. Being able to attack every player at once in multiplayer is pretty cool. Getting one or two (or more) extra enter the battlefield effects is just gravy.
The main downside to this is it doesn’t work well on a Legendary creature, correct? Actually, despite having to sacrifice the new token copies that enter, any enter the battlefield abilities still trigger. Because of how the Legendary rule works, you can choose to keep your original Legendary on board. Also, because these tokens are forced to be sacrificed, they trigger “when it dies” effects, which for certain Legendary Creatures, such as Kokusho, the Evening Star and Vela the Night Clad, is a big deal. Ordinarily, you wouldn’t get “when it dies” effects since the tokens are exiled at the end of the turn. But, with Legendary Creatures, the rule actually benefits you when it comes to Blade of Selves.
However, there is one card that has made Blade of Selves much more useful by removing the Legendary rule altogether. This card is an artifact printed in the Kamigawa Neon Dynasty set called Mirror Box. This Box makes it so the legendary rule doesn’t apply to permanents you control, as well as giving +1/+1 to each of your Legendary Creatures. Then, each nontoken creature you control gets +1/+1 for each other creature you control with that name. In particular, Gisela, Blade of Goldnight has benefited from the interaction between Mirror Box and Blade of Selves, allowing Gisela to duplicate, triplicate, or even quadruplicate, and deal massive, likely lethal damage to opponents.
Still, most of the time you’ll want to use this Equipment on non-Legendary creatures that have enter the battlefield abilities that you can abuse. Four mana seems like a bit of a steep equip cost, but it’s worth making free copies of creatures. With Eternal Witness, you can get one, two, or more extra cards back from your graveyard each time that Witness attacks! Being an artifact, there are hundreds of creatures that this Equipment will work well with and it can fit into any deck. Since these tokens must be exiled at end of turn, decks that have sacrifice outlets can benefit, as well.
There are so many options with Blade of Selves. Yes, this Equipment is only good in multiplayer games. But this includes any multiplayer format that supports Legacy-legal cards such as Archenemy or Planechase, not only Commander. Since it can fit into any deck being a colorless artifact, this is a super fun, sometimes game-ending, inclusion in a wide array of decks.