[3.X] How to: Creating a Spell.

[Yael]

I've seen that you CAN create a new spell in-game, however, I don't know if this is legit, or if it is; you need a special feat or certain skill check.

Is this legit?

[Aharon]

Yes. Information about it can be found in the DMG. It is only guidelines, though, and they are not very detailed. A lot of it will be based on DM decisions.

[Big Fau]

There is a formula for creating new Psionic powers on (I think) page 98 of XPH, and it's trivial to just translate that to magic.

[Bhaakon]

It's legit, and you don't need any special feats. All you need is money for the research, two successful skill checks (one spellcraft, one knowledge, DC 20+ double spell level), and a willing GM.

A lot of GMs are reluctant to allow creating new spells, and for good reason. It's easy to make overpowered spells, or to accidentally allow seemingly reasonable spells that create powerful synergies with other abilities.

Consider Paragon Surge (http://www.d20pfsrd.com/magic/all-spells/p/paragon-surge), a seemingly benign, even forgettable, spell...except for the (almost certainly) unintended consequence of allowing sorcerers access to nearly their entire spell list via the Expanded Arcana (http://www.d20pfsrd.com/feats/general-feats/expanded-arcana) feat.