Gabriel acquired this artifact of the elves during Castle of Freya, Episode 3. After attuning to it, he discovered that the item is sentient and telepathically demanded that he swear to uphold the highest ideals of heroic valor. Agreeing to do this, it began to tell him tales of the many elven heroes who had born it before him, including itself, even when he sleeps through his dreams… Apparently Ossandrya, the spirit bound to the broach, was a great warrior who helped Corellon drive the drow into the Underdark during the Last Battle of the Spiral Tower.

In game mechanics terms, the item has these properties:

• The wearer has resistance to poison.
• The wearer can cast the cantrip Guidance (PH page 248) as an action by consulting telepathically with Ossandrya.
• The wearer gains proficiency in Acrobatics if they don’t already have it.
• The wearer gains a +2 to their Constitution score while attuned to the emblem, to a maximum score of 22.
• Once per long rest, the wearer can give themselves or an ally within 30 feet advantage on an attack roll, saving throw or skill check by retelling tales of glory he/she has heard from Ossandrya to inspire them.
• When the wearer sleeps, the Emblem replays past adventures in the character's dreams. The hero must make a Wisdom save DC 10 or wake up with one level of exhaustion (PH page 291). This level can be removed by a short rest.
• The emblem has a special hatred for the drow.