Spellthief Lux's E
Normally minor visual differences don't make much of an impact on gameplay for skins, but in the case of this one, it most certainly does. I didn't notice it on the old rift, and that might be exactly the problem, but on the new rift it seems like the E is completely invisible and even the red circle indicator for the spell doesn't show up at all because of the new colors of the rift. If I'm not mistaken, skins aren't supposed to have gameplay improvements, and an invisible spell to me is definitely a gameplay enhancement and down right broken for how the spell works. Please keep this bumped so that we can get Riot to address this.