Background is a subtype of Enchantments, and flavorfully represents a Commander’s backstory — or at least an aspect of it. They do function as normal enchantments, so if they are in a deck they can be drawn and cast normally, although as they specifically only affect Commanders, it’s very unlikely you’ll ever encounter one in any other format. But the …

Myriad is a creature-based multiplayer mechainc. I mean, you could play it in a 1-vs-1 game, but it wouldn’t do a whole lot of anything. Here’s why: When a creature with Myriad attacks, for each opponent other than the one you attacked, you create a token copy of the myriad creature that enters the battlefield tapped and attacking those opponents. …

Devour is a mechanic that flavorfully does exactly what it says on the tin, and makes some truly huge threats as a result.  Devour appears solely on creature cards, and represents some monster getting larger as it, well, devours other creatures. When a creature with Devour would enter the battlefield, you may sacrifice any number of creatures. If you do, …

Retrace appears on Instants and Sorceries, and is a mechanic that lets you get a lot of use out of those spells. If a card with Retrace is in your graveyard, you may pay its mana cost and discard a land from your hand to cast it from there, still obeying all normal timing restrictions. However, unlike a lot of …

Casualty will usually appear on instants and sorceries, although as Ob Nixilis, the Adversary shows, it can appear on any card type. It will always be written with a number next to it, and functions as an optional additional cost. Whenever you cast a spell with casualty, you may sacrifice a creature that has power equal to or greater than …