SRD:Beckon The Frozen
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Beckon the Frozen ( Frostburn, p. 47)
Creatures you summon are infused with cold energy and have the cold subtype.
Augment Summoning (PH) , Spell Focus (PH) (conjuration)
When you summon a creature or creatures using any summon spell, you can opt to summon a version of the creature from an extraplanar frostfell. If you do so, the summoned creature gains the cold subtype, and its natural attacks deal an additional 1d6 points of cold damage. Creatures with the fire subtype can never be enhanced with the cold subtype in this manner.