The Secret Lair either includes new versions of iconic Magic: The Gathering cards, with art tied to a specific collaboration, or entirely new cards, and Sonic got both of these
Giving your creatures wither makes combat a nightmare for your opponents, letting you trade away creatures and draw cards
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Use it with cards like Sire of Stagnation, Hostage Taker, and Agent of Treachery for a particularly mean deck, or with cards like Eternal Witness, Uro, Titan of Nature's Wrath, and Wood Elves for a fast, ramping deck
Similar to cards like Platinum Angel, you need to make sure you can protect it once its in play, but this gives control decks a way to close out games without relying on Omniscience, which everyone is prepared for these days