A friend at school and I were talking about it, and I was wondering how many passive item effects can work on Garen's E? I would've asked my friend but he is the kind of person who puts 6 Warmog's on a tank and says it is legitimate so uh...yeah.
Well, his E is a spell, so it procs Rylai's and spell vamp as an aoe. It allows for crits at a 50% damage decrease as well, but that's about it.
There is no limit to the amount of passives that can work. The important part is E counts as a spell so:
(1) You get 1/3 value of spellvamp because it is an AoE spell
(2) Procs slow from 
(3) Procs DoT from 
Even though you shouldn't be building those items, they do work. More useful items that work with the E are 
& 
. Lizard elder isn't optimal but does work better than the AP items. Wicked Hatchet is solid.
