User blog comment:Yordleportal/Essence Reaver theory/@comment-25055281-20140705172834

"Is ER part of any optimun ADC item build?"

Probably not, ADCs that can skip it and rush IE or invest for late game with BotRK are quite good. And even Trinity ADCs can manage their mana costs.

"Is ER viable on any functional build?"

Yes, and you can find some examples. Like Ezreal with ER+Trinity into Last Whisper (with Lucidity? 25% CDR for 3-2s Q) for a great mid game with constant Q poke on a poke comp (the falll off lategame...but if you win it early). Not all the examples are ADCs.

"Is ER interesting on experimental fun builds?"

Yes indeed, imagine Jinx with this and Runaan's, rokets allwais togled (more than 4-16% of an standard AA damage into mana if the 3 bolts hit) for an AoE ADC (Kayle does it with MagicDamage)...Get IE for AoE crits.

Thing is many items see little use because they are not optimal on standard builds...and that's ok