1. To drink blood, use the Bite Victim ability. Remove their headgear first.
You must remain still while draining blood.
2. Danger! If you walk in space, starlight will burn you to a crisp.
The chaplain is your nemesis. Avoid him and the chapel.
3. New powers unlock when you collect a certain amount of blood (as indicated below).
Every time you use a power that isn't free, it depletes part of your blood reserve.
0 - Cancel Stuns, also replenishes stamina.
0 - Glare, short stun.
0 - Hypnotize, long stun.
200 - Vampiric Vision, thermals.
200 - Diseased Touch, give someone grave fever.
300 - Mist Form, walk through walls.
300 - Radio Interference, jam nearby headsets.
400 - Summon Bats, summons angry bats.
400 - Chiropteran Screech, stun people, break glass.
600 - Cloak of Darkness, cloak in unlit areas.
600 - Cancel Stuns Mk2, also heals.
800 - Enthrall, make someone your mindslave.
1000 - Full power, no harm from chapel. X-Ray vision.
4. For more information, please consult the wiki.