Hello, here is how the item works.

Just got told my build was wasting stats because I was going over 40% cdr. I had Trinity force, Essence reaver, and warrior jungle item. ER gives 10 flat, then it only gives an extra 10 with 20% crit from TF, so thats 20% CDR from ER. Then 10% from TF, and 10% from Warrior.

I had an enemy player absolutely FLAMING me about how trashy I was because I cannot count. Please, just, please.