The red crystal can grant the wearer Invulnerability from everything from physically and mentally attacks and magic and scientific attacks and being Invincible.

Origin:
A evil Sorcerer created it to be Invincible against his enemies but his Downfall was he took it off when going to sleep and someone came during the night and killed the Sorcerer.

Location:
The villain warlock possession(the one who killed the the other Sorcerer(Formerly)

Sentinels of Justice base trophy room(present)

Image: