Crystallized Fire

Source
Dropped by various fire elemental themed creatures in Northrend zones, such as: Found while mining Titanium Veins.
 * Raging Boiler in Borean Tundra
 * Seething Revenant or Wailing Winds in The Storm Peaks
 * Unbound Firestorm in Halls of Lightning
 * Raging Flame in Cauldron of Flame in Wintergrasp

Harvested by Engineers, using the Zapthrottle Mote Extractor upon Cinder Clouds in Sholazar Basin, Dragonblight, and Wintergrasp, and Steam Clouds in Borean Tundra and Sholazar Basin.

Crystallized Fire as an ingredient

 * (1 Eternal Fire = 10 Crystallized Fire and vice versa)

Alchemy

 * Mighty Frost Protection Potion

Blacksmithing

 * Corroded Saronite Edge
 * Corroded Saronite Woundbringer
 * Honed Cobalt Cleaver
 * Saronite Mindcrusher
 * Saronite Spellblade
 * Savage Cobalt Slicer

Tailoring

 * Azure Spellthread
 * Frostsavage Belt
 * Frostsavage Boots
 * Frostsavage Bracers
 * Frostsavage Cowl
 * Frostsavage Gloves
 * Frostsavage Leggings
 * Frostsavage Robe
 * Frostsavage Shoulders

Smelting

 * Smelt Titansteel