Talk:Rylai's Crystal Scepter/@comment-75.142.233.167-20120904172643/@comment-68.190.33.136-20121002150510

Not exactly multiplicative: calculation goes starting (baseMS + flatMSBonus/penalty) * (1+percentBonus) * (1-percentPenalty).

However, there is a soft cap: If MS >= 490, MS = (MS*.5)+230, and if MS <= 220, MS = (MS*.5) + 110.

So let's say we have Lulu casting Whimsy on a foe with a Rylai.. Whimsy is a flat MS penalty (and one of the few, if not the only one). Assuming the foe has a base MS of 310 with a boot of speed (Flat bonus of 50), we have (310 + 50 - 60), and as Whimsy is a single target, it will proc the full slow. So without any other factors, the new MS is (310+50-60) * (1-.35), or 300 * .65 which is 195. As MS is less than 220, actual MS is 97.5 (i.e. 195/2) + 110, or 207.5. This is an significant improvement over just using Whimsy, which would result in MS of 300.