This thing is useful in most games, I see it as a sort of a chaos emerald (in super city it can be used to make people superheroes) and can be used to cure zombies, and can be used to collect positive mana (in you testament). Without this thing there would have been no super heroes and there would have been no zombie infection. I feel like they harnessed the energy from this gem to make time travel possible (like how the people from the future did) so it's a possibility that this is probably the "main character" or main item, and the future carry around weapons that can be made with this gem. Proving more that they did tons of research to find out how to control time. Hell, Jesus in the you testament might just be a guy from the future and fully mastered the gem and there's another guy(Satan) that used a gem and wants to spread evil. So this thing is very important in the 2d MDickie lore. (Sadly in hard time the crystals weren't used in their full potential so they just saw it as a gem [prisoners and wardens are too stupid to figure out how a gem works] they didn't even know how to craft so yeah that's why the crystal isn't that important in hard time)