Final answer:
The phrase is an example of personification, attributing human qualities to the heart, an abstract concept.
Step-by-step explanation:
The phrase "a dripping dagger held in the fist of a shuddering heart" is an example of personification. This figure of speech attributes human qualities or actions to objects or abstract concepts. The heart does not literally shudder, nor can it hold a dagger; thus, the heart is being personified.