• System Options
• Long-Distance Modifiers
• College Correspondences
• Effects of Planes on Magic
• The College of Gate Magic
• Magic Items

• ...see also "Saving Throws"

System Options

I would recommend that you use the standard GURPS magic system presented in GURPS Magic and GURPS Grimoire. It's a good system, well supported with scads of spells, that works together smoothly with the GURPS mechanics. The rest of GURPS Planescape is written assuming you are using the standard GURPS magic system. Of course, as always, the GM (or even players) may want to create new spells of given colleges (or even whole new colleges?). I may eventually list some here. There's nothing wrong with using AD&D for inspiration for these new spells, but do try to create spells that work with the GURPS magic system. Note that GURPS Grimoire, if for no other reason simply because of the Gate Magic college, is recommended in addition to GURPS Magic for a Planescape game.

While GURPS Magic is fine for more beginning sorts of characters, it has been pointed out to me that Planescape is enough of a high magic setting that for more powerful characters GURPS Magic becomes somewhat underpowered. There is an excellent solution to this problem that doesn't require rebuilding GURPS Magic from scratch; use the optional Unlimited Mana (Umana) rules of S. John Ross. This is really just a minor tune-up to the GUPRS Magic rules, and it fits in well with the rest of the GURPS system, but it does give more experienced mages the ability to occasionally command greater magical energies. Right now, I think that the default Thresh and Recover rates, as well as the advantages for increasing same, work well. However, this may change in the future. I do hope eventually to provide a Planescape customized calamity table.

If you would rather try to convert the AD&D magic system over to GURPS, I refer you to GURPS Runelands (and especially the magic chapter). For my games set in the Silent Runelands, I converted the 1st edition AD&D magic system to GURPS. You're still on your own deciding which "college" a spell belongs, to, but it should get you on your way with a conversion. Again, I recommend not bothering with this, but just using the magic system created for GURPS. Even though I use GURPS Runelands for my current games in the Runelands, if I ever get around to running a GURPS Planescape game, I'm going to use GURPS Magic and GURPS Grimoire.

And, of course, as always, you're welcome to use a different magic system altogether, or to completely make up your own. Want only Rune magic? Go for it. Want only improvised spells? Go for it. You might want to think once or twice about the implications specifically with respect to the Planescape setting, but there's nothing stopping you from running wild. Again, though, you're on your own; my version of GURPS Planescape here is written assuming the standard GURPS magic system.

Long-Distance Modifiers

Because Planescape is a setting where mages might want to cast spells that cross planar boundaries, one must consider the effects of such spells on the long distance modifiers. Instead of the table on p. M10, use the following table:

Distance	Modifier
<100 yds	0
<1/2 mi	-1
<1 mi	-2
<3 mi	-3
<10 mi	-4
<50 mi	-5
<100 mi	-6
>100 mi on same plane	-7
1 plane removed	-8
2 planes removed	-9
3 planes removed	-10

College Correspondences

The books of Planescape describe the effects of various locales on specific colleges of Magic. These are the colleges from the 2nd edition AD&D rules. The table below lists each college of magic from GURPS Magic, and lists the corresponding AD&D college which should be used to determine how a given location effects it. Note that I may eventually list the effects of certain plains on certain GURPS colleges; in all cases that will supercede what you would conclude fron consulting the table below.

Notice that none of the GURPS colleges map to AD&D's "wild magic." The GM should consider if any individual spell of any college might be described as wild magic; if so, she should consider using the effects of a location upon wild magic for that spell, rather than the one from the table below.

GURPS College	Corresponding AD&D College
Air	Elemental Air
Animal	Alteration [1]
Body Control	Alteration [1]
Communication & Empathy	Divination?
Earth	Elemental Earth
Enchantment	Conjuration/Summoning?
Fire	Elemental Fire
Food	Invocation/Evocation [2]
Gate	Alteration
Healing	Alteration [3]
Illusion and Creation	Illusion/Phantasm [4]
Knowledge	Divination
Light & Darkness	Alteration [1]
Making & Breaking	Invocation/Evocation
Meta	Conjuration/Summoning
Mind Control	Enchantment/Charm
Movement	Alteration
Necromantic	Necromantic
Plant	Alteration [1]
Protection & Warning	Abjuration
Sound	Invocation/Evocation
Technological	[5]
Water	Elemental Water
Weather	Elemental Air or Water

Notes:

1. "Alteration" is a more general category than some of the GURPS colleges which have been mapped to it. A GM should pay attention to the specific college and plane in question (e.g. the Beastlands in particular might have some bearing on the effectiveness of Animal Control spells). Some Light & Darkness spells might better be considered Illusion/Phatasm spells.

2. Some spells are more appropriately Alteration, some are more appropriately Invocation/Evocation. The GM should use his judgement with respect to individual spells and their effects.

3. The GM may wish to ponder the effects of the planes on Clerical magic when considering the Healing college. Note that some spells might rightfully be more Necromantic than Alteration.

4. Creation spells are more rightfully Invocation/Evocation. The GM should use judgement in each individual case.

5. Most of the Tech college is not appropriate in the Planescape setting. The GM can optionally get rid of it altogether, or consider spells on a case by case basis.

Effects of Planes on Magic

The simplest way to model diminished and enhanced colleges of magic is to state that the given plane is Low Mana for those colleges which are diminished, and High Mana (or even, in rare cases, Very High Mana) for those colleges which are enhanced. In the latter case, the GM might want to give a small bonus to spell ability (+1-+5) as well. Use the college correspondence table above as a general guide, but the GM should use his judgement as to whether a spell would be affected on a case-by-case basis.

For those colleges whose spell effects are "modified" by a plane, the GM should just use his good sense. Many of the descriptions in the TSR Planescape products already contain general descriptions (e.g. what happens to fire-based spells) rather than mechanistic rules for specific spells, so you can apply the descriptions just as easily to GURPS spells.

Later, in the chapter on Planes, I list effects on magic for some of the planes, converted into GURPS terms. Don't expect that page to ever be comprehensive; as always, GM judgement is the most useful tool. However, I do (for instance) suggest a way of modelling the magic suppresive rings of the Outlands under the standard GURPS magic system.

THE REST OF THIS PAGE STILL NEEDS UPDATES FOR GURPS/4E

The College of Gate Magic

For obvious reasons, the college of Gate Magic is particularly relevant to the multiverse of Planescape. By and large, the GURPS Gate can be used unmodified. It is up to the GM if she wants to allow the time manipulation spells; if so, they should be extremely rare, expensive, and hard to find. Be aware of Planescape's restrictions on spells that require "extra dimensions"; several of the spells from the Gate college fit this description.

Be aware that many of the portals on the plane are in fact not enchantments, even if they were created with the assistance of magic! As such, players can't go shutting down the Lady's portals by casting "Remove Enchantment". This is doubly true for conduits, which are probably much more spacetime topology effects than actual gates.

Modified Spells

The following GURPS Gate spells should be modified to fit with Planescape: (Note: still needs to be verified for GURPS/4e)

Planar Visit

This spell is probably not appropriate, except perhaps specifically with respect to the Astral and Ethereal planes.

Plane Shift

This spell is roughly the GURPS equivalent of AD&D's Teleport Without Error, except that it requires changing planes, and is plane specific. Assume that, as with AD&D's Teleport Without Error, the caster can go to any location he wants on the destination plane, subject to the usual teleportation restrictions as to how well he knows the place he's teleporting to. If the caster doesn't specify the specific destination, or has no way of homing on to a specific position on a plane, then the destination is at the GM's whim. This spell also has as an added prerequisite Teleport.

Control Gate

Most portals cannot be moved with this spell; since Planescape portals generally have to form within an archway or an enclosed space, that wouldn't make sense. Gates can be temporarily closed with this spell, and it stands in for the AD&D spell Gate Ward.

Create Gate

This spell is not actually modified, but do note that it costs 200 energy to create a gate to another plane. This means that it's not the sort of thing players are going to be doing on their own very often! Note that this spell will not work within Sigil.

New Spells

Major Plane Shift (Regular)

This works just like Plane Shift, but this single spell can transport the player to any other plane. This spell may also be used as an enhanced Teleport spell which has no skill penalty for arbitrary distances. This spell is the real stand-in for AD&D's Teleport Without Error.
Duration: Permanent
Cost:

Range	Cost
<100 mi	Use "Teleport" table (p. m71)
>100 mi	10
1 plane removed	12
2 planes removed	15
3+ planes removed	20

Time to cast: 10 seconds
Prerequisite: Magery 3, Teleport and four different individual plane Plane Shift spells
Item: Any item; cost 4,000.

Astral Spell

Magic Items

Weapons

It is my opinion that a +1 magical enchantment to both attack probability and damage is worth more in GURPS than it is in AD&D. Normally, I will take the total number of "plusses" a weapon has and divide it between (in GURPS terms) Accuracy and Puissance. So, what may be in an AD&D book a +3 sword would be in GURPS Planescape a sword with +2 accuracy and +1 puissance (or vice versa). This of course gives the GM freedom to design swords whose magic is entirely Accuracy or Puissance.

Various Planescape products describe how the number of "plusses" of a magic weapon decrease as the weapon moves from its plane of origin. There are two options. If you want to tie magic weapons more closesly to their home plane than is even the case in AD&D Planescape, assess the penalty against both Accuracy and Puissance. If you want to tie them less closely to their home plane, then alternate the penalty between Accuracy and Puissance, much as plusses are alternated when converting AD&D weapons to GURPS.

Spell-like Magic Items

For things like wands which duplicate the effects of standard spells, use standard GURPS magic items, as described in GURPS Magic. Don't bother trying to convert the AD&D items over. Just make a GURPS magic item that does qualititively the same thing, and don't worry too much about whether the power level is absolutely identical.

Miscellaneous Magic

Many magic items have effects which are written as verbal descriptions rather than mechanistic rules. Those don't need to be converated at all; they can still do the same magical thing. In some cases, things will need to be converted into GURPS terms; the GM should use his good judgement. (For instance, in almost all cases the number of hit points of damage something does will need to be greatly reduced.)