Seems to me this depends a lot on the character's tone, why s/he eats hearts, etc. But it's an evocative turn of phrase, so I could not resist.
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When you eat your victim's still-beating heart, roll +weird.
On a 10+, it is delicious. You hold 2.
On a 7-9 it is bitter. You hold 1.
You may spend your hold at any time to:
* Know one thing that its owner knew.
* Do one thing as its owner would do it.
* Appear for a moment as its owner appeared.
* Track those who share its heart's-blood.
* Let their heart bleed instead of yours.
(Take +1 forward or 1 less harm, when appropriate.)
On a miss it is poison. Its owner demands a task of you, and you take -1 forward until you complete the task, or purge the blood.
All unspent hold is lost when you eat a new heart. If the last heart you ate tasted of poison, you must come to terms with its demand before using this move again. Any hearts eaten meanwhile are filling, but taste of ash.