Enact a rule entitled “Mastery”:

Every spell has a required Mastery level (a non-negative integer) for each domain used in casting the spell. This Mastery level is recorded in the form “[Domain: Mastery level]” next to the spell name.

For each domain within a spell, one Mastery level is added for every 20 energy added to a spell due to that domain. For example, if a spell allowed the caster to gain one Mastery in Fire and any apprentice to gain one level in arcane the required mastery would be [F:0, A:2]. (Fire adds 10 = 5*1*1 energy to the spell, and Arcane adds 45=5*3*3 energy to the spell).

In the case that a spell includes the “Any Domain” parameter, the Mastery level for each domain should be calculated independently of this part of the spell, and then calculated as if that element were in the place of that parameter. The mastery level is then recorded as [Domain:Mastery w/o “Any Domain”||Mastery level w/ “Any Domain”]. T For example, a spell allowing any apprentice to gain one level in any domain and allowing the caster to gain one level in Fire would be recorded as: [F:0 || 2,T: 0 || 1, A: 0 || 2] (omitting the domains that have 0 for all parameters). When casting this spell, the apprentice would only need Mastery 2 in Fire if they chose the any Domain to be Fire.

An apprentice may only cast a spell if they meet the given Mastery level requirements for each domain (and the optional requirements for the specific domain they choose for the “Any Domain” clause), unless otherwise specified by the rules (e.g. flourish).