It's really quite telling that short of a few long hard looks at the rules for Witchfire looking for gaps to exploit, there has been no praise what so ever for the Maleceptor. It's so awful that even players who champion underpowered units aren't willing to give it a second look.
GW really dropped the ball on this one, which is a shame because the concept of a monster with psychic tentacles is interesting and the model looks great.
Thinking about the Maleceptor and its fluff, two things stand out. One, the previously mentioned psychic tentacles that brush over the minds of other creatures and melt their brains. Two, it is "the Shadow in the Warp made manifest". This just screams "anit psyker unit" to me, which is something the Tyranids have lost out on a bit since the changes brought by 7th Edition.
I've cooked up a revised (and much better) version of the Maleceptor below. C&C welcome
The Maleceptor is a terrifying Tyranid organism rarely seen on the battlefield and is believed to be created only when the Tyranid invasion faces resistance from powerful enemy Psykers. Space Marines of the Grey Knights chapter also reported creatures similar to the Maleceptor on the devoured world of Shadowbrink when the Tyranids faced a Daemonic legion, but these reports are impossible to verify following the destruction of that world. The Maleceptor is a large quadrupedal organism with a bloated armoured torso housing six additional brains which amplify the effects of the Shadow in the Warp to unbearable levels rendering he use of otherworldly powers even more difficult and dangerous. Mortal Psykers have taken their own lives rather than endure the presence of a Maleceptor on the battlefield, and psychically-sensitive races such as the Eldar struggle to remain conscious when facing this monster. Even more fearsome, the six sub-brains within the Maleceptor possess a malign instinct to directly assault enemy Psykers, and ethereal tendrils of power reach out from the Maleceptor to shred the minds of any Psykers within reach. So preoccupied are these poor victims with simply holding onto their sanity under the Shadow that they are powerless to deflect the alien's lethal mental assault.
Maleceptor: 205 points
Brood: 1 Monstrous Creature
WS BS S T W I A
Ld Sv
3 3 5 6 6 3 3 10 4+
Weapons: Scything Talons
Special Rules:
Synapse Creature
Shadow in the Warp
Psyker (Mastery Level 2)
Psychic Powers: A Maleceptor always knows the Psychic Overload power (see below) and generates one other power from the Powers of the Hive Mind.
Warp Shield: The Maleceptor is protected by psychic barriers similar to those of a Zoanthrope, and has a 3+ Invulnerable save.
Manifest Shadow: A Maleceptor's Shadow in the Warp special rule affects all enemy units within 24", rather than the usual 12". Additionally, enemy units with the Psyker, Brotherhood of Psykers of Daemon special rule trying to Deny the Witch against any Psychic Power cast by a Maleceptor can only successfully Deny the Witch on a 6+, regardless of any other modifiers that would normally be applied.
Psychic Overload (Warp Charge 2): Psychic Overload is a Malediction with a range of 24". The target unit must take a Leadership test on
3D6. If the test is failed the unit suffers a number of wounds equal to the number the Leadership test was failed by, with no armour or cover saves allowed. Vehicles are treated as having Leadership 10, and if a vehicle fails this test then it instead suffers a Glancing Hit with no cover saves allowed.
The idea is a) to boost the survivability of the Maleceptor by increasing its Invulnerable save to something more appropriate considering its cost and then b) to really home in on the anti-Psyker concept by combining the effects of the -3 Leadership from Shadows with a Leadership-based Malediction that is specifically harder to stop if you are a Psyker or a Daemon. Other targets are still possible, even vehicles, but they are far from optimal making this unit something you really want to use to hunt enemy Psykers.