PuRplE
Black clover is a good choice, as I can boost overall power of group members. Also can you let aster train with he's power? From what I understand he is an winter spirit so he can use other abilities and not only ice manipulation. So he should be able to freez time, absorb/drain heat from living bings and objects, control winter wether, some degree of water manipulation, ability to control North winds, also he should be able to change freely between spiritual and physical forms. This is soma I can think of on a spur.