“The Archons are the links between the Fallen and their Servitors. We break those links, we break the Fallen.”
Riksis is an Archon who once ruled the House of Devils. When the Houses fell, the Fallen Leadership had nothing to rule like before, but they could still worship a Servitor and command small groups. Sepiks Prime is the Servitor he followed, and it’s not known if Riksis or Sepiks Prime were involved in the battle at Twilight Gap.
This high Archon wasn’t your normal Priest. He’s larger than his Fallen brothers and had no shield, unlike other Captains. Riksis would collect the skulls of Guardians he’d kill and probably offer them up to his Prime, Sepiks. He commanded a group of Fallen at Dock 13 and protected a jumpship that contained parts important for a Guardian to achieve transport off Earth.
There are theories that Riksis is Aksis, the final boss in the Wrath of the Machine Raid, but it really depends on how you interpret the Grimoire Card for Aksis. We know that Riksis is dead (killed during the “Restoration” mission). The Aksis Grimoire states, “A former Archon Priest, Aksis has submerged himself in SIVA’s apotheosis and emerged as Archon Prime.” This sentence assumes that Aksis was already alive and he submerged himself, in which case Riksis couldn’t be Aksis. However, Sepiks was augmented with SIVA and reborn, so it is possible that Riksis could also be Perfected. If the House of Devils look to reclaim their status on Earth, then they’d need their most brutal Archons.
Sources: Grimoire Cards House of Devils, Aksis, Sepiks Perfected, and Riksis, Devil Archon at www.bungie.net.