Clarification about the Sorcery System

[Anaraxes]

Originally Posted by DangerousThing

Do you mean the difference between known spells and improvised spells? There should be no difference between the two.

Well, there's certainly a difference between "known" and "improvised" -- though not in how you make success rolls to cast.

"Known" and "learned" mean the same thing -- that that you've spent character points so that you're not improvising the spell. "Learned" is not a separate term of art in the Sorcery rules. "Improvised" spells have not been purchased with character points. They're just invented on the fly whenever the sorceror feels the need.

As was mentioned, Sorcery is built on existing GURPS rules. If all you've read is the Sorcery book, some of those underlying principles may not be familiar. Sorcery does tell you how it's all built. But the short form is that spells are all abilities built from Advantages, as per Basic and Powers; Sorcerous Empowerment is a Modular Ability, which is the mechanic that lets sorcerors improvise spells; and known spells are individual pre-designed abilities, which are all in a Alternative Abilities group with Sorcerous Empowerment. (Sorcerous Empowerment is required to be the most expensive abilities in that group -- that is, cost more than any single spell -- which makes sure that all the known spells are bought at 1/5th cost for the AA, while Sorcerous Empowerment is always the one full-price ability in the group.)

Sorcery has little (if any) all-new rules made up just for the sake of that system. So, most questions about how spells work can be answered just by seeing how that spell would work if it were a singular ability built for the character. Range penalties are the standard speed/range table, because that's where Advantages and abilities built from them often start. You can change the kind of range penalty by adding the appropriate Enhancements or Limitations to the spell when you design it -- but those modifiers would be in the stats block that describes the spell.

Whether or not you need two Maneuvers to cast a spell doesn't depend on whether or not it's known. That comes from the underlying AA (Alternative Ability) rules. AAs have one active ability. You can switch to another ability in the group -- but that switch requires taking a Ready or Concentrate Maneuver to do. Abilities with an activation roll, including sorcery spells, take one Concentrate Maneuver to cast. So, it's not really two Maneuvers to cast -- it's one Maneuver to swap spells, and a second to cast the new one. If you happen to cast the same spell twice in a row, then for the second cast, it's already the active member of the AA group. So you don't need the Maneuver to rearrange that AA group. Just cast the spell. To cast a different spell, you'd have to rearrange the AA group (one Concentrate) and then cast your spell (another Concentrate -- if that particular spell/ability needs an activation roll).

Not all abilities in GURPS require an activation roll, which is why some spells say "Casting Roll: None", while others might say something like "Casting Roll: IQ". The underlying base Advantage (Innate Attack, Telekinesis, Terror, Affliction, etc) determine whether or not an ability will need an activation roll, though that need can be added as an extra Limitation (see "Requires (Attribute) Roll" in Powers, for instance).

So, in the Sorcery book, you'd have to check the description of each spell to see what kind of casting roll is listed. There's not a general rule along the lines of "all known spells require a casting roll" or "only improvised spells require a casting roll".

(That kind of consistency might be desirable for some systems built out of the same pieces. See PK's other book, "Psi Powers", for an approach which does start with the assumption that all abilities have a casting roll on some associated skill -- and so builds each ability to add a roll if it didn't have one, or alter the basic definition from an attribute to a skill if needed.)