There have been three people that have control over blood. 1) Rai, 2)The Lord, 3) Rai's Brother. This is my guess but I think Rai's brother is alive and if that Red Aura is a blood field then it might have been created by Rai's Brother.
Arlen Grace is alive. She has immortally like 10 Family Leaders/Zahard. She tried to commit sucide but could not die so she started to look for a way out of the tower and met the God outside the tower according to her diary. This is my guess that she is inside the tower because as she claimed...