Hm, interesting. While I agree the draw-back is very dangerous, it may be less dangerous than you think. Pandemonium rarely kills more than 4 creatures when it's used, which is only -20 HP for +4 cards. I think it's fair; losing 20% of the HP you start with to go through 17% of the deck you start with. Plus, at the maximum, this card can only do 40 damage in one turn (definitely not enough for an OTK). But this only occurs when you have 0 cards in your hand, and most of the time if you have 0 cards in your hand it's because you're overproducing quanta and you'll have enough quanta to play the 8 cards you just drew from Blood Oath.
The base mechanic is to mitigate CC used by your opponent, this is non-negotiable. I don't know if the cost of HP is best for a Death card, so that can be changed. However, I refuse to remove the CC mitigation and then proceed to over-complicate secondary mechanic just to create a Death permanent that can only draw cards.
Your point on the theme is valid. Perhaps this card needs a theme rework.
maybe "blood altar" "styx" or something like that
you could lose 6 hp for each creature you kill and 3 hp for each creature your opponent kills (or viceversa) or something like that
