To defeat demons faster, stand in a doorway and fire projectiles at them then feed on their souls. This works best if they hit a wall as you fire.
Defeating Faustus
Keep blocking and sidestepping his attacks while finding open spots for attack until you get about one quarter of his life down. Then, he will run off and enter a room will large heaters and mist around them. When Faustus jumps on to a heater, proceed towards the beginning of the mist trail that leads to the heater and pull the switch to hurt him. Keep repeating this procedure until he jumps up on to a chain, then run to a corner of the room and stay there until Faustus jumps down . He will now try to jump and kick you from far away. If you sidestep his attack, he will hit the wall and will be vulnerable for a few seconds. Keep repeating this until he is dead.
Go through locked door to real Soulreaver
After the intermission sequence when Raziel gets the Soulreaver and he gets controlled by it, Mobius will close the door. Defeat everyone down where you had to turn to the different world, then go in the middle of the lock to go through.
Invincibility
When you have all the Elemental Reavers, go to the castle where you began. Use the Fire Reaver on the floor. It has the sign of the Fire Reaver and is orange. Plunge the sword into it, then get the light. Use it on the door, then keep going until you get to a room where the Soul Reaver is located. Mobius will appear and insult Raziel. He will then take the Soul Reaver and be invincible. Note: You will suck blood instead of souls and also fight all Raziel's brothers and Raziel when he was human.
Invincibility
Press [Enter] [Left] [Left] [Up] [Down] [Right] [Action]. Raziel will speak to confirm correct code entry. To disable this effect, press [Enter] [Right] [Right] [Down] [Up] [Left] [Action].
Save health from Raziel's Soul Reaver gauge
If you notice your Soul Reaver gauge is getting high and want to save your health from it, switch to the Spectral Realm. It will deplete almost instantly.
Defeating demons...