Mostly meant for cosmetic purposes.
NetherRealm has finally opened up on the microtransactions in Injustice 2 in the form of Source Crystals. Contrary to what you’d expect from the new gear focus, these Crystals are meant primarily for cosmetic purposes.
Source Crystals can be spent on Premiere Skins, skin shaders and the Transform Gear function. Premiere Skins are essentially new looks for characters that can change their appearance and voice. Shaders are different colour palettes for existing gear (as seen above). Transform Gear is essentially a transmogrification feature, allowing you to change a piece of gear to look like another while keeping the same stats.
It was noted that none of these options are pay to win, though it is possible to use Source Crystals to level up other characters to level 20 if you have one character at that rank. NetherRealm noted that, “This is optional and won’t affect gameplay or game progression.”
Injustice 2 is out on May 16th for Xbox One and PS4.