[Robert]

According table on CRB page 162, the spell "mana barrier" either creates a mana barrier on the physical plane or on the astral plane.

• Can the mage choose the plane the barrier should be at time of casting? OR
• Is the barrier created on the plane the mage is when casting, meaning only a pysical mage could cast a physical mana barrier and only an astral projecting mage could cast an astral mana barrier.
• Is the barrier created on the plane the mage is when casting, meaning only a pysical mage could cast a physical mana barrier and an astral projecting mage and a physical mage with astral perception could cast an astral mana barrier, due to the physical mage with astral perception beeing dual-natured.

CRB page 161
"Mana barriers on the physical plane ... act as solid  barriers  to  spells,  manifesting  entities,  dual-natured  entities,  spirits,  and  active  foci."
and
"Mana barriers on the astral plane ... stop astral movement..."

• Does a mana barrier on the astral plane stop dual-natured things (manifesting entities, dual-natured entities, active foci)?
• If yes, what is the difference between a mana barrier on physical or astral plane, as both basically stop the same things? I assume an astral mana barrier will definitively stop spirits, so the only unclear item is whether an astral mana barrier would stop spells cast on the physical plane.
• If no, how can I rationalize that there is an astral mana barrier and it does not stop the astral from of e.g. a dual-natured shape shifter, but it does stop e.g. the dual-natured shape of a materialized spirit? Would we need to identify a "home plane" for each entity (e.g. shape shifter home plane is physical thus not affected by astal mana barrier, spirit home plane is astral thus affected by astral mana barrier)?

[cuidaBeja]

I'm a bit rusty on this but both barriers should stop dual natured creatures on the physical plane. A ghoul can't separate or deactivate their astral and physical forms, so neither plane will halt their progress.

Most other scenarios pretty clearly show the differences between the two.

Things with no astral signature but a physical presence will pass through astral barriers but treat physical barriers as barriers. An astral barrier will not stop a grenade, or instance. An astral barrier will not stop a street Sam from walking up to you with a katana.

Magical things with limited physical presence should be able to go through a physical barrier (if you can see. I don't remember how opaque they are). Mana bolt or stun bolt should be able to pass through, while indirect spells splash on their surface. A manifested spirit can be stopped with a physical barrier, but they can manifest themselves on either side (if they have a couple rounds) by going into the astral to bypass it.

All spells exist in the astral, so an astral barrier should block all magic across it. Even spells on the physical plane exist on the astral plane. This means that an astral barrier across a corporate entrance is going to attempt to dispel or deactivate sustained spells as well.

As I said. I'm rusty and never really specialized in magic, but there are plenty of differences between the two. Hopefully a Hermetic will show up who actually studies the stuff instead of playing by feel and memory.

[Xenon]

If you are using your physical perception then you cast it on the physical plane.
If you switched to your astral perception then you instead cast it on the astral plane.

But the easiest is probably to just house rule that Mana Barrier Spell is always present on both the Astral Plane and Physical Plane at the same time. Like a regular Ward.



The main purpose of casting a mana barrier spell on the physical plane seem to be to make it harder for an opponent magician on the physical plane to cast spells at you.

If you wish to protect a location from astral entities you would typically use one of the rituals (like a Ward). Or build a medicine lodge.