Pokemon TCG: Sword and Shield Chilling Reign - Elite Trainer Box
It will release on June 18th.
The set should be comprised of cards from S5a Matchless Fighters and S6 Silver Lance / Jet-Black Spirit.
The name comes from the fact the last two sets feature Ice Rider Calyrex and Shadow Rider Calyrex. Their sets haven’t been officially revealed yet. The two Calyrex will appear as Water or Psychic-type Pokemon V and VMAX.