Widen Spell (Metamagic)

You can cast your spells so that they occupy a larger space.
Benefit: You can alter a burst, emanation, or spread-shaped spell to increase its area. Any numeric measurements of the spell’s area increase by 100%. Spells that do not have an area of one of those four sorts are not affected by this feat.
Using this feat increases the magic point cost of the spell by 5.

featmetamagic