Chains of Mephetis (Blue)

You may play this from your banished zone. If you do, it enters the arena with a doom counter.

At the start of your turn, destroy this unless you remove a doom counter from it.

If a hero would draw a card during an action phase, instead they banish the top card of their deck and may play it this turn.

Blood Debt

Rulings

From the Dusk till Dawn release notes

You may not play this from your banished zone if it is face-down.
You may choose to destroy this at the start of your turn even if it has a doom counter on it – as removing the doom counter is optional.
This has a replacement effect that replaces the draw with a banish. You are not considered to have drawn a card if it is banished instead this way.
If you would draw 2 or more cards, instead you banish that many cards from the top of your deck and may play each of them this turn from your banished zone.

Keyword notes

Blood Debt - Blood Debt is a new keyword existing on Shadow cards. Shadow cards can inflict a loss of life to access a greater power. At the end of your turn, you lose 1{h} for each blood debt card in your banished zone.

You only lose life at the end phase. Players do not have priority during the end phase.
If you have multiple cards with blood debt, you lose 1 for each instance of blood debt at the end of turn.
Only face-up cards banished with blood debt counts and will lose you . Face-down banished cards have no effects or stats.