Simple Lissandra Passive
I've heard Riot is working on some "exploding frozen statue" passive for Lissandra, and I think people are looking forward to that.
It sounds interesting, but it also sounds complicated and probably even pretty busted.
Why not do something simple?
They could easily just have her deal bonus magic damage, a small amount of true damage, or give her bonus magic penetration to targets that have had their movement impaired by her crowd control.
Simple