The top of Onyx can only be accessed by the Gers lift itself, which comes up the fall line that Onyx follows.
The Onyx can be joined part way by taking the Jais, accessible from the Desert Blanc chairlift, the Grand Platieres gondola (with a schuss and a pole) and the Diamant Noir chairlift (ditto).
This piste is full of bumps, lumps, holes and dips as it follows the fall line, with scrub and bush occasionally poking through to provide an extra challenge.
Moguls seem to appear out of nowhere and at times it takes the form of a gulley.
It is a long run so it' only really suitable if you are fit and have stamina, and that goes for coming back up the extremely long button lift as well.