I’ve always thought that Augment Summoning was lonely, and I wanted to see other Feats linked to Spell focus in the other arcane schools. So here we go – this is a rough sketch, feel free to take and adapt for yourselves:
Prerequisite: Spell focus (abjuration)
When making a d20 roll related to dispelling a magical effect, the caster can take 20.
Prerequisite: Spell focus (divination)
The duration of all divination spells is extended to concentration +2 rounds where that duration exceeds the listed duration. For example, scrying lasts for 1 minute/level or concentration +2 rounds, whichever is longer.
Prerequisite: Spell focus (enchantment)
Charm spells cast by a person with this Feat are more powerful than normal. Opposed Charisma checks are not required except for the most extreme commands, and the subject of the charm spell will undertake dangerous actions which fall short of suicide. Lastly, when the charm spell ends, the victim will not have a clear memory of having been magically coerced unless she succeeds at a will save at the spell’s normal DC.
Prerequisite: Spell focus (evocation)
Then caster chooses an element in which she specializes. When she casts evocation spells with this element, the deals +1 damage per damage die rolled. For example, a fire-specialized elementalist would deal 5d6+5 damage at 9th level when casting fireball.
Prerequisite: Spell focus (illusion)
Illusionists who take this feat are able to create more persistent figments using spells like Silent Image or Major Image. These illusions persist even after the caster ceases concentrating on them. As long as a figment persists, however, the caster loses that spell slot until she dispels the illusion or it is dispelled with a successful will roll due to disbelief.
Prerequisite: Spell focus (necromancy)
All undead created by a necromancer with this feat are affected as if they are on desecrated ground, including +1 to attack and damage rolls as well as saving throws. These undead also receive +1 hit point per HD.
Prerequisite: Spell focus (transmutation)
When the transmuter casts a spell which augments the ability of it’s target, this bonus is raised by +2. So, for example, Fox’s Cunning increases Intelligence by +6.