4/5
I actually think this card is UP in an average deck but possibly OP with some comboes.
The reason I believe it is UP is because hp is precious and because of the randomness of damage dealt to the owner (I am not really fond of randomness). Without shields it is a great card, but with shields I am not sure it worths the risk to damage yourself via an unblockable kind of damage only to have it dealing 3-4 damage per turn, you will need some sort of healing just to play this card. I also will feel bad for the poor AI where it will keep spamming these while you have a Dim chain or a Hope, leading to an even earlier death.
However, it brings more interesting targets for Nightmare, Mitosis & Empathic bonds (Bonds to heal the damage dealt by your own Sidhes) and even a
duo with only
quanta sources and some Holy Flashes to heal the Sidhe damage. Can't be abused by Fractal due to the damage dealt by the ability, so this is actualy a huge plus for its design. Due to the randomness and the big risk that makes this card more situational than it should be, I cut a star and it gets 4/5. Still, an awesome job, Rippy!