I can't find a description for the functionality of this rune when used in conjunction with maximum CDR. How does the Ultimate Hat stack with cooldown reduction? You get a total of 15% reduced ultimate cooldown from the rune alone.
Primaquarius4 votesIm guessing it reduces the base cooldown
LightningShado1 votesIt stacks. It's not multiplicative. You would be able to get a maximum of 60 percent CDR with this rune and one that gives you +5 percent maximum CDR.
Profirix5 votesMultiplicative would be the reasonable option. Additive is the broken option.
LightningShado1 votesOk, 15 percent off the base cooldown and then 45 percent off that would be less. Ok you're right.
Profirix1 votesThe reason I want to know is because I'm trying to theory-craft for Cho'Gath. I would always take resolve primary for obvious reasons, but I am debating between precision and sorcery for secondary. Ultimate hat makes or breaks this option because his ultimate is such a huge part of his kit.
Bittum1 votes(I know this thread is a bit old but if anyone else wants to know)
Tldr: It seems to be multiplicative sadly.
I thought the rune might be OP with teemo since he can stack it up so fast, found that he could get shrooms down to 9.4s charge time, and have up to 35 shrooms on the map at once, but you can get it down to 12s with normal 40% cdr so its probably not worth...
Anyway the maths: lvl3 teemo ult has 20s charge time normally with 45% cdr + 15% from Ultimate hat was 9.4s
If it was additive: 20 * (1-0.6) = 8s cd
If it's multiplicative: 20 * [ (1 - 0.45)*(1 - 0.15) ] = 9.35s cd (which rounds to 9.4s)