Btw, I was thinking as a minor possibility, which is not much different to what you suggested OT;
What if I implemented the passive "Liquid shadow/vampire" to Archangel?
It is essentially similar to your first suggestion of draing hp, but combined with my idea of infested,
since liquid shadow effect is associated with
in metagame, It would technically make sense,
This may solve the problem with Eclipse and Blessing, as healing won't work on it, so eventually, the user can be tempted to transform it into archangel before it dies from poison.
Would this work?