Yeah so basically the longer he is in battle the more stacks he gets off of this mythic. Each stack grants 7% more healing and shielding which totals to 35% by the end on top of that it heals other allies. Its also a really cheap item only costing 2500. The downsides of going this is its damage is low and the easy counter play. It was fun when i tired it and healed half my HP is one battle but my enemy laner rushed antiheal which sorta ruined it. I was still able to cast a large shield tho.

One other thing to note is that healing so good that you win in your ult 10/10 no matter how fed the enemy was.