This makes no sense to me at all. Not lore wise nor kit wise. Like... how does it compliment the kit or the laning phase or ganking or anything? Maybe team fights if you're already winning. She is like an ice goddess is it really that hard to come up with a fitting passive that compliments her kit that has arguably 1 really offensive move? It's an awkward passive to have, it feels like ivern on ARAM.
Boards wanted a new Lissandra Passive so they gave her a new one.
From Lizzandra's lore:
"—Lissandra sacrificed her sisters and the allies they had gathered, entombing the Watchers beneath a glacial barrier of magical ice that could never be melted."
"The truth is perhaps more sinister, as she uses her elemental magic to twist the power of True Ice into something dark and terrible, entombing or impaling any who would reveal her deepest secrets."
Her entire kit and lore revolve around ice magic and her ultimate is an ice-coffin. I think the passive is fitting from both standpoints. It's destructive in teamfights and landing a kill can give Lissandra some time to breath as enemies have to watch out for the explosion.
