1)
What is "Kis'i" that Hashem will put in Eilam?
1.
Rashi: It is his Matzor 1 .
2.
Radak: Since I will eradicate its king and officers, they will understand that it is from Me, it is as if My throne is there, and I will appoint a king over it. Megilah 10b expounds that the king that Hashem will destroy is Vashti, and "Sarim" refers to Haman and his 10 sons. All will know that the salvation at that time is from Hashem.
3.
Malbim: Since they will not have a king or officers (I will eradicate them), I will rule over them.