Cooperative Magic (Magical)Modifier
Your assistance makes spellcasting far more potent.
Prerequisites: Spellcraft 4+, Knowledge (Arcana) 4+
Benefit: When you are casting a spell, you can use the help of other spellcasters. Thoses caster need to be at a maximum of 5ft of you and usally form a Circle around you (but other shape exist as well depending on traditions). You can lead a maximum of 1 Spellcaster per Intelligence Bonus you have. Those Spellcaster need to spend a Standard action to help you cast your spell, but they dont need to expand any spell slots. Each Spellcaster that know the spell provide you with a +2 Bonus to DC and Caster level. For Spellcaster who dont know the spell but can cast a spell of that level they provide a bonus of +1 to DC and Caster level. The Bonus to Caster level can never be more than the original Caster level and the Bonus to DC is capped at the normal DC - 10. Your ally dont expand any slots for helping you that way, but they spend an action to contribute to the spell power.
Essentia: You can lead +1 Spellcaster and increase the max DC and Caster level possible by +1 / Essentia
Example: A Wizard level 13 with intelligence 20 join with the party Cleric and Sorcerer of the same level. They all try to cast Banishment. The Caster level will increase to 16 [+2 for the Cleric and +1 for the Sorcerer who dont know the spell, the maximum caster level possible was 26] and the DC to 24 [to a max of 32]