The cosmic entity, Eon, designed an artefact to protect the universe called the Quantum Bands. Eon routinely bestows these bracelets to those he deems worthy to safeguard the cosmos.
The person who normally possesses the Quantum Bands is a SHIELD agent called Wendell Vaughn. Despite graduating with full donors, Vaughn was dismissed by SHIELD agents for his lacking a killer instinct. When he was chosen by Eon to wield the Quantum Bands, Vaughn became the superhero, Quasar.
While he possesses these armlets, Quasar can tap into the energy from the Quantum Zone; a realm where all energy in the universe originates. With the bands, he can create shields, fly through space, communicate with cosmic beings, and control all forms of energy.
He can render the Bands invisible to hide his identity and has programmed them so he is immune to telepathy. He can open a wormhole and perform a Quantum Jump to teleport vast distances in an instant.
Although it sounds like his power is limitless, the Bands are vulnerable to magic and Quasar will become exhausted if he overuses them.