As of CLv1:
- counter spell targeting player effect work
- regen creature work but only if you cast it at regeneration phase (if player cast it before it will reject the mana into mana pool as shown in the pic below)

- if AI has some creatures and the player doesn't, if player cast it for the
Fog effect, game will ask for target creature, if player hit cancel the mana will be rejected into the mana pool and the spell considered as cast (go to gy), then if player cast again another
Dawn Charm game will generate an endless legacy card error.
