What it does
"Allure of Slaanesh" isn't an official Magic keyword or ability—it doesn't appear on any card, and there's no rules text governing it. It may be a confusion with cards from the Warhammer 40,000 Commander decks (which do feature Slaanesh-themed cards, like Slaanesh, God of Excess), but "Allure of Slaanesh" specifically isn't a recognized mechanic.
If you encountered this name, double-check the card—it might be a custom/proxy card, a misremembered title, or from an unofficial set. Slaanesh-related effects in the official 40K decks typically revolve around forced sacrifice, attacking incentives, and "Tempting Offer" (where opponents choose whether to copy an effect, granting you a bonus if they decline).
For an accurate ruling, share the exact card name and oracle text, and I can break down precisely how it works in Commander.
