To replicate: cast Mana Reflection, then use Monster Rider. Mana Reflection will be canceled immediately. Affects all three classes: both archmages and bishop. Imagine one of the worst buffs in the game getting even worse
It's because you can't deal damage while on a mount, it does the same to power guard and summons won't attack either.
Yea, I dislike when power guard on my paladin gets taken away because I used my mount. Also some related weirdness, when my paladin uses mount and gets hit by mobs, it has a chance to aggro them, but nothing indicates why that happens. My suspicion is that it's Guardian proccing but not showing the effect/not stunning the mob etc etc. There's no real reasoning or good points in that thread Inusama linked. Unless someone can enlighten me, I don't see a justifiable reason why we should keep mounts functioning this way. I guess one would say 'go say this in Feedback' as this is not a bug...
