Grubberfly's Elegy

Description
''Contains the gratitude of grubs who will move to the next stage of their lives. Imbues weapons with a holy strength.''

When the bearer is at full health, they will fire beams of white-hot energy from their nail.

How to Acquire
Gifted by Grubfather after freeing all 40 Grubs

Trivia
The beams of energy provided, and the charm as a whole, is likely a reference to The Legend of Zelda, in which on multiple occasions the character could fire ranged attacks from their sword, and in most games required full health.