Powerful, shiny gemstones that act as power sources for Internals. Every internal has their own individual Master Crystal (including Basalt) that grant them their power and special ablities. If their crystals break, something really bad will happen. Its never been seen before. A Master Crystal can also be gifted to a Wolf Pack Member is they do something really good.
NOTE: StevePiPi can also siphon the energy from a Master Crystal to gain (and even amplify) its power, despite him not being an Internal.

As the king of crystals, the Ultimate Crystal can control, revive, or limit the powers of every Master Crystal. It can also break special seals or mystic locks, which, in Basalt's case, lets him unleash Internal Rest and gain ultimate power. The Ultimate Crystal can still be hijacked by corruption, however...

Believed to be fake, the Final Crystal unleashes never seen before power and gives Basalt the strength of Internal Reality. Said to be lost in a forgotten dimension. in a near-indestructible chamber. However, this is just a myth.

A synthetic Master Crystal created by Nightmare. Despite it not being the real deal, it acts as a personal power source for him. 

The Hollow Crystal was a master crystal before corruptions got corrupted. Once they were corrupted, it was overtaken by corruption.

A refillable canister holding Soul-Fuel which powers Internals and their soul-related abilities and is used to fuel vehicles in Skill City but cannot be used to fuel Astro's ship, which uses a source that is only available from his planet. Internals cannot bloom or stellar charge without Soul-Fuel or it will lead to a Darkness Form

Chan's planet's form of currency

Astro's form of currency