Cocoon

Cocoon '(コクーン, Kokūn) is the term used to describe the shape of energy that surrounds a Zoid during the evolution process in Zoids: Chaotic Century. The evolution of Zoids usually occures through the power of an Organoid, and in some cases, an Organoid and Ancient Zoidian.

Chaotic Century
Van Flyheight's Shield Liger and Raven's Geno Saurer evolved into the Blade Liger and Geno Breaker respectively at several different points in the anime, Van's having evolved because of Fiona and Zeke's combined effort, and Raven's through Shadow's efforts.