As unlikely as it may be what if Belkar is related to Serini?

The climatic fight forces the Order to begin the same ritual to seal the gates and its Belkar who sacrifices himself to save creation?

It could be the only way to defeat whatever safeguards Serini has requires one of the adventurer's to sacrifice themselves to gain access.

Well Belkar is fated to die, what if his sacrifice causes Serini to reveal herself after witnessing the same tragedy that cost Kraagor his life?