Burst of Celerity

 is an active skill that can be taught to Sorcerers at level 48. It cannot be ranked up.

This skill as active skill was removed in sorcerer revamp (NA: Spellbound patch, EU Portentous Rebirth) in October 2016. Instead it became passive skill that raises sorcerer's attack speed permanently 30%.

can be performed with a disc by the Sorcerer. Note, this skill is going to completely alter your gameplay. In Tera, attack speed basically means animation speed. Therefore, even spells with an instant cast time would actually take time to be carried out. What Burst of Celerity does is speeds up that animation, such that even your instant-cast spells would fire off much faster.

This will allow you to dump ridiculous amounts of damage on bosses, so two things will happen: 1) you will draw very high aggro, so your party must have a lancer who knows what he's doing and 2) your mana pool will be depleted extremely quickly.
 * For 1), if your lancer messes up, you can choose to stun/sleep/immobilize the boss (although this often fails, because another party member would immediately hit the boss, thus ending the effect), or cast Stone Skin (if you are level 60) to drop all aggro. If nothing is available, keep running, and keep using slowing skills (ie. Glacial Retreat, Hail Storm).
 * For 2), take precautions by buying glyphs and crystals that decrease your mana consumption, and take mana pots when needed.

Rank table
To obtain, one must find a Magic Instructor and pay a certain price of gold.

Glyphs
To glyph, a glyph must be obtained and learned only once. At level 60, a character has 50 glyph points available to spend on all available sorcerer glyphs. Most glyphs, specifically common glyphs can be purchased from a Glyph Master, while fine glyphs must be looted from enemies.

(Disclaimer: As NPC shop prices vary depending on a variety of factors, the prices below are subject to variation. Only take them as benchmarks.)