I was playing kayle and I noticed one E empowered auto gave 3 fervor stacks. I wondered why and it was obvious for 2 fervor stacks (Auto attack and E counting as a spell) and had no idea where the third came from until I auto'd while bandit was on cd and noticed I only got 2 fervor stacks.
You get 1 stack of fervor for auto attacking a champion (2 for melee) and 2 stacks for damaging an enemy champion with an ability.
So for the first situation, you got 1 stack for the auto attack and 2 for your E, for a total of 3 stacks.
For the second situation, I'm going to guess you auto attacked while your E wasn't active, which makes Kayle melee, thus granting 2 stacks.
