魔石(ファイナルファンタジーVI)
Magicite is the leftover remains of an esper. For the esper's magical power to be fully drained, it must transform into magicite. The esper's soul remains anchored to the magicite, and can communicate and be temporarily summoned back into their living incarnation. They are equippable by the player characters in the menu, where they can teach magic, summon the esper, and grant stat boosts. 
"Wiki Link":[https://finalfantasy.fandom.com/wiki/Magicite#Final_Fantasy_VI]
magicite