Tyranid Exocrine

If the link to the Hive Mind is severed as a Body Damage Table result, the Exocrine will Nest. When Nesting, the Exocrine will remain stationary and fire at the nearest enemy (individual, squad or vehicle) in its shooting phase. It can defend itself in close combat as normal

If charged by an enemy causing fear, take a psychology check. If passed, fight as normal. If failed, automatically break if outnumbered by charging enemy. If enemy does not outnumber, half the units WS (rounding up) in the first turn of combat and cannot fire overwatch. 
If charging enemy unit that causes fear, must take psychology check. If failed, cannot charge and must remain stationary for the turn (but can fire normally). 
If hit by a weapon that causes fear it must take a Break test regardless of casualties inflicted by the weapon

Immune to all psychology. Cannot be affected by fear, terror, or any of the psychological factors in the Warhammer rulebook. 
Still affected by Break tests like other troops

Tyranid Vehicles are targeted as a Vehicle

Bolt Of Change, Force Dome, Hammer of Fury, Eldrich Storm, and Assail affect Tyranid vehicles  as vehicles. Vortex, Aura Of Decay, Aquiescence, Pink Fire Of Tzeench, Executioner, Kop Dis and Da Crunch work as normal. The Leadership test-based Powers (Domination, Smite, Scourging, Beam of Slaanesh, Pavane of Slaanesh and Storm Of Wrath) will apply to any Tyranid vehicle that is outside the range of a Hive Node (Hive Tyrant,Tyranid Warrior)

The Exocrine uses its Ram Value for any damage inflicted by it in close combat. Because the Exocrine is so large, the extra dicem and +1 WS bonuses for additional attackers do not apply in any close combat with the Exocrine 

When a Tyranid vehicle rams or charges another vehicle, work out damage to the other vehicle as normal. For the Tyranid vehicle the location that actually touches the other vehicles is hit on a 4+ and other locations are hit on a 6+. Work out damage for any hit locations as normal

1: Foot
2-4: Body
5-6: Bio-Cannon