"On self cast: Lissandra encases herself in dark ice for 2.5 seconds, healing for 100 (+x%), increased for 1% for each 1% Health she is missing, and becoming untargetable and inbulnerable but unable to take any actions."
Little makes sense here. You have a flat base value, then a % ratio (% of what? Maximum health? Current? Missing?), then a grammar error (_for 1%_ should be _by 1%_).
I suggest a considerable rewording of that portion of Lissandra's ult tooltip.