This is a replacement system for the psychic powers in Genestealer, which I consider too 'magicky'.

Librarians and Psykers get 10 psi points per level, as described in Deathwing.
'The Psyker' will refer to an active librarian or hybrid psyker.
When using a psychic power, the psyker must spend a minimum of 1 psi-point. They may spend up to 6 points without danger. If more than 6 points are spent, then the psyker is endangering his own mind: Roll one die and add the number of points spent over 6. Consult the Argh, My Mind Is Burning! table, with the psyker as the target.

Argh, My Mind Is Burning!

total	effect
0-4	No effect.
5	Stun; Target becomes prone.
6	Confusion; The target performs actions using 2 AP, controlled by the opposing player. The target may not attack his allies or perform anything suicidal (including self-destruct or using psychic powers). If the target is a hybrid confused by a librarian, any blips withing the target's LOS are converted.
7	Paralyze: The target cannot use any AP until the attackers next phase. He can still defend in combat and use CP.
8	Warp Beast: Place a warp beast adjacent to the target. It has 3 AP but acts after each players turn. It moves towards the nearest model and attacks in close combat with 3 dice. Ranged weapons attack it as if it were a genestealer. If there is no room to place a warp beast model, it attacks the target as it enters. If the attack is successful, the target is removed and the beastie takes it's place. If the attack fails, the warp beast returns to the warp and it is not placed on the map.
9+	Smite: The target's brain pops - remove the model as a kill.

Switch, 1 AP, Free
Open or close one door anywhere on the map for 1 psi-point. A door will not close onto a blip or model.

Blast, 2 AP, LOS
Target a model or cargo within line of sight, and push it back one square per 1 psi-point spent.
If the target is cargo:
If it is moved into another item or wall or a flame template, it becomes rubble.
->If it hits a model, the model is knocked prone and the cargo becomes rubble
If the target is a model:
->If it is pushed back into cargo or rubble, the cargo becomes rubble and the model is knocked prone.
->If it is pushed into another model, then that model is pushed back.
->If it is pushed a wall then roll d6 for each 'push' into the wall. It is killed on a 6 and knocked prone on a 5.
->If it is pushed into a flame template, roll to see if it is killed as if it had been hit by the flamer.
If the target is a psyker: It may counter the blast with psi-points on a one-for-one basis. The attacker may bolster the attack with extra psi-points and 1 AP.
The defender has one more opportunity to counter with more psi-points. If he does not counter then he is hit with the full effect of the blast; pushed back by a number of squares equal to the total number of psi-points put into the attack.
If the blast is nullified, then the energy is released as a shockwave centered at the half-way point between the battling psykers. The range of this shockwave is equal to the total psi-points used attacking. It pushes everything back to the edge of it's range or until it hits a wall, as described above.

Prescience, 1 AP, -
For every 2 psi-points spent, +1 to all shooting and close combat attack rolls until the psyker's next turn.

Scan, 1 AP, Free
For each psi-point spent, convert one blip. Starting with the closest and continue outwards.

Channel Force, 0 AP, Requires Force Weapon
+1 to close combat roll per 1 psi-point spent; during attack or defence.

Shield, 0 AP, Requires Force Weapon
Uses up 1 psi-point; When the psyker is the target of a ranged attack, Shield allows him to parry the attack as though it were a melee attack.

Aura, 0 AP, -
Used whenever this unit is killed. It may also be used when a friendly unit is killed by an area effect or Interrogation that also effects this unit. Roll two dice to determine how may psi points are used up. If this unit does not have enough psi, the aura fails and the target is killed.

Interrogation, 2 AP, Blind
This is the basic psionic attack for all psykers and libriarians
Target one model with 12 spaces of the psyker. Models in the same board section as the target may also be targeted for 1 psi-point per additional model.
Decide how many psi-points to spend in attacking.
If a target is psychic or if a psyker can see a target, they may spend psi-points in defence without using up AP. If this occurs, the attacking psyker can bolster the interrogation with more psi points and 1 AP. The defender gets one more opportunity to bolster his defence.
Roll one dice, adding the attacking psi and subtracting the defending psi. Consult the Argh! My Brain Is Burning! table to see how the targets are effected. All models are effected with the same result.
Note that the attacker will have to roll on this table as normal if he used more than 6 psi-points.
Negative results are possible; simply take the absoulte value and apply it to the attacking psyker instead!
Example: A librarian spends 2 AP to interrogate 5 genestealers in the adjacent section. This costs 4 psi-points. He decides to put 2 psi-points into the attack. There are no defending psykers. He rolls one die (a six) and adds his attack; the result is 8 - warp beast. A tear appears in space-time and five warp beasts (one for each target) pour from the warp into the section!
The librarian spent a total of 6 psi-points so is only just spared having to roll on the Brain Burn table himself.

Use the solo movement rules as described in Deathwing.

A hybrid will go on overwatch if it cannot make an attack, if it's weapon is able to go on overwatch, and if a Marine could enter it's LOS during the Marine phase.

When a psyker is activated it move towards the Marines as normal. Once within 12 spaces, roll one die.
1-3 The hybrid advances as normal.
4 The hybrid will attempt to Interrogate the nearest model or group of models in the same section.
It will use the minimum psi-points required, plus 1d6. If required to bolster the attack, it will do so with an extra d6 psi-points.
5 The hybrid will advance, using Prescience if it is able to make an attack.
6 The hybrid will advance, using Blast instead of an attack, using 1d6 psi-points. If requried to bolster the attack, it will do so with an extra d6 psi-points.

If a psyker hybrid has a force weapon, it will always use Channel (using 1d6 psi-points) and Shield.
They will always attempt to nullify blasts using the required psi-points, and counter interrogations using 1d6 psi-points for the initial and bolstering defence.
They will always attempt to perform an Aura if killed.