how to determine "base skill" for Ritual Magic

[Roko Joko]

The energy cost and ritual requirements of a spell (4e B236 and B237) are determined by the spell's base skill. With Ritual Magic, exactly what counts toward that? The Magery bonus? The prerequisite penalty?

[Refplace]

Originally Posted by Roko Joko

The energy cost and ritual requirements of a spell (4e B236 and B237) are determined by the spell's base skill. With Ritual Magic, exactly what counts toward that? The Magery bonus? The prerequisite penalty?

Yes to both.
Magery increases effective spell skill.
The Prereq count us a penalty to the skill default from the Core skill (Usually Thaumatology or Ritual Magic).

Use the free Spell PDF to help with preq counts.

[Roko Joko]

Originally Posted by Refplace

Yes to both.
Magery increases effective spell skill.

Do you mean it increases base spell skill? The rules emphasize that base skill is what matters here:
"If your base skill with a spell - ..." -B236
"...'skill' refers to base skill, not effective skill." -B237

[Celjabba]

What count toward base or effective skill is a bit of a blur, but afaik:

Base skill is modified by :
-Attribute and whatever modifies attributes.
-Talent (including power talent, Magery, Power investiture.)
-Advantages like voice, charisma, ...
-Disadvantages (hidebound, ...)
-skill intrinsic bonus/penalties that always apply when a skill is used in a specific way (Specialization, "Prereq. count" in the case of ritual magic).

Effective skill is modified by
-equipment.
-situational modifiers.
-combat modifiers (maneuvers, hit location, ...)
-familiarities.

Conditional Advantages like destiny, and perk like weapon/equipment bond, or fashion sense, are a grey area. I could see argument for counting them toward either base or effective.

[PK]

Celjabba is right. Magery always adds to base skill, and a technique penalty (whether magical or not) always subtracts from base skill.

So if you have IQ 13 and Magery 3, it costs 8 points to buy Ritual Magic-16 (a relative skill of IQ+3). If you're then trying to cast a spell with 4 prerequisites, your "base skill" for that spell is 12.