Just as the Thanatou had said, they had to wait and observe the portal and see if the Mother knew anything about it.
They had to be careful not to fall into any trap.
However, they couldn't wait forever.
The more the Thanatou stayed in hiding, the more his power was threatened and the more it would be harder for him to gain control of his Realm.
The Thanatou couldn't believe his mother was throwing a useless tantrum just because he had killed his sister. If she had stayed in line and not interfered with his activities of ruling, then he wouldn't have killed her.
She brought this death upon herself.
When he would gain his throne again, he would give his Thanis warrior that was in love with her, another Thanks woman who would be obedient. She would make him forget about his sister and he would remain loyal by his side forever.