Crystal

Crystals are seen in most Crash games as an energy source, a lot like gems. They have been used in the series since Crash Bandicoot 2: Cortex Strikes Back. In state of fact there are 25 slave crystals ,one Master Crystal and the Super Big Power crystal, these Crystals were mostly used for evil to control all of Dr. Cortex's machines and gadets but now mostly used for good to help Crash Bandicoot save the world from the Time Twister Machine and stopping the Elementals. However, there are 28 Crystals in Crash Bash. In that game, the Crystals apparantly have the power to change the environment in the stages, in addition to changing their rules. After Crash Twinsanity the Power Crystals were replaced with the Mojo that was used to power Cortex's machines and to create his mutant army.

Trivia
The Power Crystals, are most likely based off the Amethyst Crystal a type of quartz mineral. Due to their shape and complexity of color only being in the violet varity.