Solte is one of the new characters in Fate of Heat 2. He is a Ring Craftsman who is able to refine Rings from either rainbow-colored stones or unknown stones. Originally a Belladonna Lily member, he deserted them when he noticed their plans.
Role in Fate of Heat 2
While escaping from the Belladonna Lily, he meets Tsuna, who had just traveled 10 years into the Future. From then on, he puts his Ring Craftmanship at the service of the Vongola and fights alongside them to put an end to his brother's ambition.
Role in Fate of Heat 3
Solte is only a side character. Though he can help you by creating rings from crystals/gems. He can be unlock once all the Guardians have unfrozen their Rings and once you control Tsuna once again.