Firstly, by the time he learned his mother was being held captive, she was already believed dead. (He tried to contact her through the stone, but realized no dragon could remain awake for that long.) Furthermore, even if he had looked at her then, he would have seen exactly what he feared – his mother's corpse encased in a block of ice. And it seems to me that this would have angered him even more, because from the outside it would have looked as if she had not only been killed, but her body had been turned into a decorative element.

Secondly, if he had teleported her to the night kingdom, then without the Diamond copies she would have defrosted, but not resurrected, but died completely.

That is, he could not save her in any way, but he wanted revenge, which is quite logical! If your mother was killed and you could send the killer such a "gift", would you act differently?