Question again.

Lets say the players are inside a Gellar field (on a ship that's in the Warp, or some fortress close to a Warp Rift)
How does this effect the players?
I'd imagine that they won't be able to summon Daemons, but does it affect Psykic powers aswel, harder to test, or impossible.
What about the incorperal trait? Can they still test it?

Thanks

Caboosebe said:

There's no official answer on this one way or another, but my personal interpretation is thus:

A Gellar Field acts like an artificial version of the barrier that separates the Warp from Reality - within it, a captured pocket of reality persists around a ship (with multiple ships able to overlap their Gellar Fields to allow fleets to move as one). The barrier itself is fairly thin, and while capable of containing a starship and thousands of crew under normal circumstances, undue stresses can weaken, damage or even breach a Gellar Field's effects, much as particular events can weaken, damage or breach the veil between realms.

Manifesting a psychic power or summoning a daemon through an active Gellar Field is in theory no different to summoning one into reality... the difference is in the nature of the field - a Gellar Field is a fragile construct produced by arcane devices that are poorly understood by most, and the act of breaching or disturbing it can exact a terrible toll aboard a starship. I'd actually make Tests to summon Daemons and use Psychic Powers easier within a Gellar Field within the Warp, but with a much greater risk of Psychic Phenomena and Perils of the Warp, as the psyker/sorcerer/daemonologist risks doing catastrophic damage to the only thing keeping the Warp from overwhelming the ship.

I'd completely agree. It's "merely" a pocket of reality, so treat it the way you'd treat "reality" with maybe a small dash of demon firewall.

Thank you very much, it is a point of view I hadn't considered, and eventually better then my own.

I'd also add that there are many references in the canon to the Gellar field flickering, which can be very dangerous when a ship is within the warp, as it would allow the ingress of warp entities into the vessel in the split second the field was down.

Presumably for this split second, the reality bubble within the field merges with the warp itself - another reason space travel should not be taken lightly in 40k!