How does this Mythic works?
your HP & MP are kind of pooled together but are also separate. you get +50% of your lowest current HP/MP % for damage, and you take +50% of your highest current HP/MP % in damage from your enemies. when you take damage or cast spells, it is taken from the highest of your HP/MP and when you heal or regain MP, it is added to the lowest of your HP/MP. it doesn’t matter if you have HP or MP heals, they both work on which ever is lowest.
if your HP is equal to or higher than your MP, and you take damage, then you lose HP. when your HP goes lower than your MP, then any damage you take gets taken from your MP instead. this also applies when you are casting your spells. if your MP goes to 0, but you still have HP, you wont die, I think. I haven’t tested this, but I believe you need 0 HP to die with Alchemy.
the problem is keeping your +50% damage from going down and not losing HP. the best thing to do is have very high MP so that your HP never goes down. I am not sure, as I haven’t tested it yet, but I think if you have Glasscannon +100%, your HP will be 1, but you will be at 100% HP which means you always get the +50% damage. the down side is all damage & spell costs come out of your MP. on lower floors, it might be a problem if your Build isn’t Crafted right, on higher floors, you only have to worry about getting one shot killed by monsters.
I’ve try this item and it saves me from those enemies at the PvE with DoT when the time I use it.
My question is does it works with the Mythic Sanctuary?
sure. Sanctuary activates when your HP goes down to 0. then you are invulnerable for 1 second with a 30 second Cool Down until it can activate again. it doesn’t matter if you have a Resource Mythic or not. zero HP is zero HP.