Reptos

A primitive Xenos race native to the Jungle world of Hyades IV. Reptos are described as being both simian and reptilian. They were fairly quick but on the small side, and easily killed by Space Marines and the Hyades PDF. They are sentient and intelligent enough to form plans and set traps. They have their own language. The Reptos are quite primitive and have no higher levels of technology. They may have built certain temples on Hyades. Once the Imperium arrived on Hyades they were deemed little more than a nuisance and little effort was made to exterminate them. At some point they fell under the sway of Madox and the Thousand Sons, it is unknown whether they worshiped Chaos, Tzeentch alone or were simply tricked by by the Thousand Sons. Reptos society appears to be tribal in nature and is very unsophisticated. It seems they are led by elders or possible cult leaders, we never hear them speak in any form of Low Gothic so it is difficult to tell. They may be worshipers of Tzeentch. Reptos show no demonstration of high levels of technology and appear to be at a stone age level of technology. They may or may not have built temples on Hyades.

TL;DR: Scaly MONKE Xenos used as Tzeentch CSM pawns.