Euryale's Crystallizing Grasp

You attempt to touch a creature and turn them to crystal. Make a melee spell attack against one creature. On a hit, they are restrained and their body starts to turn to crystal. A creature restrained in this way must make a constitution save at the end of each of its turns. If it successfully saves against this effect three times, the spell ends. If it fails its saves three times, it is turned to crystal, slaying the creature instantly. The successes and failures don't need to be consecutive, keep track of both until the creature collects three of one kind. When turned in this way, the crystal statue is treated like fine crystal, and will shatter if attacked. Also, any statues of creatures turned in this way appear very lifelike

 Note: Any of the creatures belongings are turned along with it if in contact, the only notable exceptions are powerful artifacts that drop from the creatures hands or packs as they are turned.