The Stone Warrior is a Ninjago minifigure first shown in Ninjago: Masters of Spinjitzu and appears in The Stone Army and The Greatest Fear Of All. In 2016, he was released physically in 70591 Kryptarium Breakout.
The Stone Warrior was a statue in a museum but was brought to life by the venom of The Great Devourer. The ninja battled it, but found it to be indestructible, so Lloyd devised a way to trick it into falling into the bottomless pit it came from.
It is unknown how, but he was somehow recovered and sent to Kryptarium Prison. He nearly escaped during Chen's attack, but was soon returned to his cell.