I see some interesting possibilities. How would this interact with Shard of Sacrifice?
You heal 5 health upon using the ability. I don't know if SoS affects Regeneration counters (you can test that with Purity, but I am 99% sure it does), but if it does, then you would take damage equal to your regeneration counters each turn.
It would be more useful to activate this card during SoS - you would gain 10 health (activating twice during the duration), then lose 3 health (assuming you didn't use it beforehand). Overall, you would have 14 more health than you would otherwise, so Cursed Pendant would help even out the cost of SoS a little. The enemy's damage should help assure that you take enough damage to pay for the steep cost. You can do the math for Cursed Amulet on your own, but I think there would only be a tiny difference in the damage converted to health during SoS.