From Sonic Retro
Thelxe is an antagonistic Voxai alien encountered during Chapter 9 of Sonic Chronicles: The Dark Brotherhood. Identified by Thebes as one of the "Overmind's elite protectors", Thelxe seems to be one of the few Voxai who willingly supported the despotic ambitions of Leucosia, Ligaia, and Riadne.
Thelxe confronts Sonic and Thebes on Voxai Colony Beta, as the Overmind prepares to send a Chaos Emerald through the Colony Alpha teleport gate. After being knocked out by Sonic's group, Thebes extracted the teleport code from Thelxe's mind and imprinted it on Sonic's, allowing the heroes to travel to the Overmind's inner sanctum. The last we see of Thelxe is as Sonic departs for Colony Alpha; Thebes stays behind on Beta, to "keep his mind on" the enemy Voxai.