What are Celerity and Haste?
A creature with Celerity or Haste is one that comes into play and doesn’t suffer summoning sickness (so it can attack and use it’s abilities the turn it was cast). Examples of such creatures are Ball Lightning, Avalanche Riders and Raging Goblin. The term Celerity origniated from the Jyhad(tm) Trading Game. The term Haste was introduced along with the Sixth Edition rules.