Master Crystal

The Master Crystal was found by Dr. Neo Cortex at the start of Crash Bandicoot 2: Cortex Strikes Back. Cortex brought it back to the new Cortex Vortex but he still needed 25 more Crystals to harvest the crystal's energy. After the Cortex Vortex was destroyed it is not seen or mentoined again in the game and has not been seen since and as such it was probably destroyed during the impact.