Taresia couldn't order the newborn Ring of Space to attack without accumulating enough battle experience first.
She knew how powerful Tezka was, and there was no guarantee that Taresia could craft another Salanoth. Forbidden Magic was a fickle mistress. Even if Taresia survived the ritual again, the chances of victory of a second Ring of Space would have been close to 0.
Taresia had spent most of her life studying Tezka's grimoires, and considered the Severed Sky array and the Eternity Seal spell her best shot at killing him, but only if Salanoth took the Suneater by surprise.
Taresia knew Salanoth had one chance and had to make it count.
Salanoth, on the other hand, had no reason to play her part in a gamble that didn't benefit her. If she succeeded, she would be forced to return to Taresia and obey her orders as long as the Fylgja drew breath. If Salanoth failed, she would die.
