I want to get some opinions to make sure I’m interpreting this right. From The Radical’s Handbook , p.135 (‘Resources’):

The Cortax

“A rough alliance of roving alien mercenaries for hire, the soldiers of the Cortax are available to the highest bidder, sometimes changing more than once or twice over the course of a conflict or even a single battle. Yet, for all their seeming fickleness, the Cortax are a highly sought after force within the Calixis Sector, for they provide an easily deniable, cheap source of soldiers with little in the way of morals or qualms about their victims. And, for Inquisitors seeking to foment conflict and war without any consideration for the eventual winner, such as the Istvaanians, the Cortax’s readiness to change sides mid-way a war only serves their purposes all the more.

What It Provides: These mercenaries can invade a planet, raid a settlement, or attack a spaceship.

Prerequisite: Forbidden Lore (Xenos).

Resource Test Modifier: +10.

Price/Cost: The Cortax accepts payment in weapons or Throne Gelt.”

So, am I correct in assuming that ‘the Cortax’ is an army of mixed xeno-types banded together for a common cause, and not the name of a new xeno species? That’s my reading, and it would be very silly for a sourcebook to introduce a new xenotype and not include its stats (or even a description) for it. There is no mention of the Cortax as a species on Lexicanum - but that’s true of a few WH40KRP -specific species with a single mention. What do you think? (And don’t be fooled by the picture on the same page in Radical’s Handbook - it was originally commissioned for the Inquisitor skirmish game years earlier.)

I've always read it as different Xenos races banding together under one banner. However the wording is not very clear.

My interpretation is based on the use of the word "alliance", implying that the Cortax are made up of very different subgroups. These subgroups for me have always been races.

The "alliance" could also refer to multiple mercenary companies of the same species working together (a bit like the mercenaries of the medieval Swiss Confederacy). It can be interpreted either way, but still I think it's clear that the name Cortax itself does not refer to any species, but to the mercenaries , regardless of whether they are one or more types of xenos.

There is no mention of the Cortax as a species on Lexicanum - but that’s true of a few WH40KRP -specific species with a single mention.

So even if it'd be on Lexicanum, it could either be only a replica of what you already know, or another fan's personal opinion.

You could of course now create an article on Lexicanum on this subject, and promote your preferred interpretation that way.