"Rank-Multiplication-Magic", abbreviated "RMM" (
Because of that, many monsters that can be Summoned through Rank-Multiplication-Magic cards have Ranks that go over 13, and thus can't be Summoned by the normal Xyz Summon. To prevent the Xyz Summons of monsters with crazy Ranks, at least 1 of the monsters used for the Summon must be Rank 4 or lower.All "Rank-Multiplication-Magic" cards share the same lore:
"Target 2 face-up [archetype] you control (1 of them must be a Rank 4 or lower monster); Xyz Summon 1 [archetype] monster whose Rank is equal to the result of the multiplication of their Ranks, using them as the Xyz Materials. (Xyz Materials attached to that monster also become Xyz Materials on the new Xyz Monster)."
Most "Rank-Multiplication-Magic" cards cause the Overlay Units of the new monster to change to a variety unique to them, such as "Rank-Multiplication-Magic Surpassing The Limits" changing the Overlay Units into bigger one.