Metamagic

Metamagic is a group of feats targeted towards spellcasting classes in general, but almost exclusively used by wizards, sorcerers, illusionists and other casters focusing exclusively on arcane magic for their survival and livelihood. Metamagic, put simply, allows a character to transcend the normal rules of magic and create effects that can be devastatingly powerful.

The Purpose of Metamagic
Metamagic is a way for spellcasters to augment their abilities in amazing ways. By gaining metamagic feats at requisite levels players can start to do truly amazing things.

Quicken Spell
Allows a spell to be cast as a swift action rather than a standard action. Using this metamagic feat a mage may cast two spells in a round, or cast a spell and then do something else. This is one of the most useful metamagic feats.

Still Spell
Cast a spell without having to move your hands

Silent Spell
Cast a spell silently by an act of will. Immune to silence attacks and good for surreptitious casting.

Spell Mastery
Give up a higher level spell in order to learn a lower level spell thoroughly enough to be able to prepare it without needing to consult a spellbook. The chosen spell will be in your inventory after you rest regardless of preparation.

Innate spell
Give up a higher level spell in order to learn a lower level magic so thoroughly it may be cast as a spell like ability at will.

Maximize Spell
All variable damage is maximized. For example a 20 dice fireball (20d6) would do 120 damage automatically.

Eschew Material Components
Cast spells without the need to use material components

Empower Spell
The spell does half again as much damage as usual.

Wand/Staff Mastery
You are able to use spell slots available for casting to power the use of a magic item instead of using up charges. You could use a third level spell slot for example to cast a charge from a wand of fireballs or a lighting bolt from a staff of power.