Crystals are the currency at the Crystal Merchant at spawn, or at /crystalmerchant while at spawn!
You can earn crystals from crates (at /crates) daily and weekly crates at spawn, as well as through voting and daily rewards!
These can also be condensed with 8 crystals for easier storage!
You can do so by using /condensecustom while the crystals are in your inventory.
If you want them back to normal, use /uncondensecustom while the condensed crystal is in your inventory!