There's a military tactic beloved by wargamers called the hammer and anvil. You split your army into two forces, the slower and sturdier of which pins down your opponent, holding them in place—the anvil—while the faster force maneuvers into a flanking position—the hammer—and then you bring the two together. If you've played Total War: Warhammer 3 as Slaanesh, you'll know they're an army with no anvil. Slaanesh is all hammer, all the time.
Which is why it's appropriate for the Keeper of Secrets, a greater daemon of Slaanesh, to appear as a red card in Magic: The Gathering's Warhammer 40,000 crossover (opens in new tab). Red's the traditional color of Magic's most aggressive cards, and usually the ones with keywords that speed up their attacks like haste and first strike.
The Keeper of Secrets has both. You don't need an anvil when you can just slam two hammers together for the same effect, right?
The Keeper of Secrets also has an ability called Symphony of Pain, which means whenever you cast a spell from anywhere other than your hand, you cause damage equal to that spell's mana cost. Keep an eye out for keywords to trigger that, like flashback (you can cast a spell from the graveyard), cascade (you exile cards from your library until you flip one with a lower mana cost, then cast it for free), and rebound (you cast a spell a second time the turn after it was cast). Or maybe the Chaos-themed Ruinous Powers deck will come with cards like Sen Triplets, which let you look at another player's hand and then cast spells right out of it. Honestly, that sounds like exactly the kind of dick move I'd expect from Tzeentch.
The Warhammer crossover will include four decks for Commander format, which is Magic's chill format where two or more players, usually four, take part in a free-for-all where each has a high-powered legendary creature to represent them in the field. The prebuilt Warhammer x Magic decks come with two options for your commander.
- The Ruinous Powers deck (red/blue/black): Abaddon the Despoiler and Be'lakor, the Dark Master
- Forces of the Imperium (white/blue/black): Inquisitor Greyfax and Marneus Calgar, Ultramarines Chapter Master
- The Tyranid Swarm (green/blue/red): The Swarmlord and Magus Lucca Kane
- Necron Dynasties (black): Szarekh, the Silent King, and Imotekhk, the Stormlord
Those 100-card commander decks (opens in new tab) will be released on October 7, but there will also be three crossover Secret Lair (opens in new tab) releases with even more Games Workshop-themed Magic cards available to order from October 17 to November 14. One will feature Warhammer 40,000's orks, while the other two will include cards based on Age of Sigmar and Blood Bowl.