Sneaking

From CMC Wiki

A monster with (Sneaking: Color) may not be blocked by a monster of the specified color when attacking directly. Sneaking works similarly to Invisible Attack, but Sneaking is only situationally useful, and adds very little onto the mana cost of a card. An advantage that it does have is that even if the opposing monsters are of the appropriate color and have Sneaking, they can't block you (whereas Invisible Attack monsters can block other Invisible Attack monsters)

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