Valiant Flame (5e Equipment)
From D&D Wiki
Wondrous Item (light weapons), artifact (fighter)
A scarlet gem that shimmers in hand like the pale cinders of cooling hearth. You feel its brittle heat wash over you, seething through your veins like serpents of liquid steel. Fury lights its icy inferno behind your eyes, and iron lends its strength to your once fading arm. Nothing will stop you now.
Acquisition: This artifact is gleaned by using the Hos'ri-ein ( https://www.dandwiki.com/wiki/Hos'ri-ein_(5e_Race) ) Well of Worlds to take command of an alternate past self, then in this past completing a campaign. Whence your other selves rise to the Hos'ri-ein plane, you may take this from them.
Effect: add 1/4 of your allies' highest attribute to your next attack, then 1/10 for the rest of the encounter.