What happens at the end of Clive Barker's Undying?

Spoiler alert!

At the end of Clive Barker's Undying Patrick the protagonist is taken away by some robed figure in a boat after he kills the final boss.

What does this represent? How do I interpret this scene?

The robed figure at the end is definitely not Otto Keisinger. If you listen to the dialog at the end Patrick says

The creature was a guardian. A sentinel of the gate to...somewhere. Somewhen. The Celtic warrior was just a sacrificial lid on a tomb that was never supposed to be opened.

The robed figure is the Celtic warrior who assisted in burying the Undying King if you remember the flashback / dream about it before.

Flashback / Dream:

Ending:

Patrick Galloway is taken away in a boat by Otto Keisinger who mysteriously survived their battle in Oneiros. Keisinger stole Patrick's Gel'ziabar stone and left Patrick at the shore. How he survived and why he rescued Patrick is not detailed, but the game revealed that Keisinger desired the Gel'ziabar stone and that's why he took it. The ending is a bit of cliff-hanger and there were talks of sequels but the game did not sell to expectations and the plans for a sequel were scrapped.

What if Otto Keisinger is a sentinel of the gate and has to oversee it for eternity and that's why he medled in the Covenant family in the first place. Because they started this curse as children and now Keisinger has to repair the evil that has been done.