Skarner Runeglaive Bug.
Skarner is able to stack an additional sheen item on top of Runeglaive. I tested this in a bot game, and I was able to deal both the on hit damage and area effects of Ruinglaive and Iceborn Gauntlet in one auto. When I right clicked a target and cast Q during the attack animation, but before the hit registered, it would proc both Sheens. This does not happen with two basic Sheens or with Iceborn and Trinity. So it must be a bug with the new item.