The Eagle Miraculous, when inhabited by Liiri, appears as a dark-brown eagle talon with a golden ring around the base. It hangs around the wearer's neck by a black filament and reaches down to the wearer's mid torso.
When in the possession of Gabriel Agreste, the talon and ring in camouflaged mode become silver-gray. When in the possession of Jess, the talon and ring become dark-gray.
The Eagle Miraculous grants its wielder enhanced superhuman physical abilities, including strength, speed, and agility. It also makes the user nearly invulnerable.
The Miraculous' special superpower, Liberation, allows the user to free a person from mental or emotional restrictions that limits their actions, such as fear of one's own power, or a code of ethics. When used for evil purposes, this leads to the person whom the superpower was used on going out of control, following their every whim without any concern for the consequences.
When Techlonizer was given the Miraculous, he was told by Hawk Moth that the transformation phrase was "Wings of Prey". According to Thomas Astruc, the reason for this is because the Miraculous uses a different transformation phrase when used for evil.
It is currently unknown why there would be a different transformation phrase for villainous intentions, as the Miraculouses were created specifically for heroic purposes, as stated by Nooroo in Ladybug & Cat Noir (Origins - Part 1).
However, Catalyst was deakumatized when she activated the Peacock Miraculous, while Techlonizer was still akumatized and still had his powers when he activated the Eagle Miraculous.
With Jess being a part of the North American team of superheroes, her Miraculous, like Ladybug's, Cat Noir's, Hawk Moth's and Bunnyx's Miraculous, is the fifth jewel to remain constantly active.
Since the Miraculous was given to George Washington it's unknown if he knew about the powers of the jewel when he became its keeper before it was put in a museum in New York.
In an old animatic of the show's theme song, the Eagle Miraculous was present before being replaced in the show proper. In the animatic the jewel was a light yellow ring embossed with an eagle facing left.
When Miracolizner used the Eagle Miraculous, he obtained the ability to fly although it's unknown how that happened and yet, it's possible due to the effect of Hawk Moth akumatizing him, it being one of the adult powers of the jewel or it was what Miracolizner desired deep down.