Spell research in the Glantri setting uses the following rules:
Researching a new spell takes 1 week/spell level and requires you to spend 1000gp/spell level on exotic magical components, ancient tomes and other assorted trinkets and gewgaws. At the end of that time, roll 4d6. If your roll is equal to or below the relevant attribute (Intelligence for magic-users, Wisdom for clerics), you successfully research the spell.
This is reduced to 500gp/spell level and a 3d6 roll if any of the following circumstances apply:
- You have attempted to research this spell before;
- You already know a very similar spell (DM's discretion);
- A spellcaster who knows a similar spell is tutoring you;
- You are studying a transcribed version of the spell (see "Spells and Spellbooks");
- You are studying the spell from a scroll.
If more than one of these circumstances apply, you may gain additional benefits at the DM's discretion, such as an easier roll or a more steeply reduced research cost. (Exempli gratia: If another spellcaster tutors you and you have a transcribed copy of the spell, the cost will be reduced even farther — perhaps to 250gp or even 200gp per spell level — though of course the tutor will command a fee for her time and effort. Even with that fee, the total cost will be lower than 500gp per spell level.)
In addition, you may research a spell partially or wholly via carousing. Each session of carousing counts as a week of spell research. A particularly good d20 roll on your carousing may make it easier to learn the spell or provide other research benefits; a particularly poor roll may have negative effects.