New pack of rules, fitting with battlefleet gothic rulebook revised
Planet devourer
800 Points
HITS..................Defence/30
SPORES.............6
ARMOR..............5+
SPEED...............10
TURNS...............special
WEAPONS
Prow Pyro-acid battery 12 @45 cm /Front
Prow Bio-plasma discharge 6 @15 cm /Front
Prow torpedoes 8 /front
Planetary Feeder tentacles 4/special @5 cm /Front
Starboard Pyro-acid battery 12 @45cm /right
Starboard Bio-plasma discharge 4 @15 cm /right
Starboard Launch Bays 4--
Port Pyro-acid battery12 @45cm / left
Port Bio-plasma discharge 4 @15 cm /left
Port Launch Bays 4 --
Though most swarms will typically contain more than one hive ship, in some circles it is believed that there is still a single ship that maintains central control of the entire collective and acts to coordinate the assault, though this cannot be confirmed. There are also unsubstantiated reports that there are a very small number of hive ships in every swarm that are much more massive than the rest. Dwarfing even great battleships, these immeasurably vast creatures arrive very late in the process of planetary assimilation and are believed to be those responsible for the method by which even the atmosphere and oceans are consumed from orbit, as the final stage of the world’s consumption by the hive fleet. Though such a gargantuan organism would explain how once lush and fertile worlds are left barren, airless and sterile, there are as of yet no recorded sightings of such a monstrous creature.
RULES
SIZE
Planet devourera are enormous battleships so big that they are subject to the Super-Masive quality.
Because of that they must be considered a defence in all purposes and they must move 10cm in a straight line each turn, no more, no less. It likewise does not have It speed reduced by Blast markers or damage. A planet devourer may turn up to 45° in every second Movement phase. The turn must be taken at the end of its second 10cm movement just like a space Hulk. A Planet devourer may not use Come to New Heading or Burn Retros special orders.
(*I suggest creating the Super-Massive quality in order to have an universal law for space hulks and planet devourers for example

MISTRESS OF THE HIVE
The following rules are intended for use in very specific scenarios, the Hive Mind would ever intentionally endanger It`s central control node.
The planet devourer is the ship that maintains central control of the hive mind, It counts as a hive ship with leadership 10 and a synapse range of 60cm. If it dies there won’t be synapse control anymore in this battle, all tyranids ships will act instinctively, Hive ships will lose they synapse range but they still can use it to themselves and ships in contact.
Due to their enormous capacity, the planet devourer can be considered to have 16 launch bays capacity. And its ordnance is considered automatically reloaded each turn.
Tyranid ships subject to Instinctive Behaviour case 7 (‘must move towards a planet’) may instead move towards the Planet devourer.
MOTHERLY HUG
The planet destroyer is just an enormous hive ship but it doesn’t have enough mass to have a gravity wells jus like a planet or a space hulk. But opposed to that tyranids ships will interact with their mother’s spore clouds just as if it had 5cm gravity well from the edges of its base. This just affects Tyranid ships in exactly the same way as a planetary gravity well and means that tyranid ships can take up a stationary orbit around the planet devourer. Objects orbiting the hive ship are moved along with it until such time as they break orbit. A ship deciding to break orbit must do so before the ship moves. In other words, no free moves!
Tyranid ships can also dock by just being in contact with the planet devourer. Dock tyranid ships will gain Extra Magazine and Augmented Damage Control qualities. They will also gain +1 spore as their mother will protect them.
PLANETARY FEEDING TENTACLES
Planet devourers are the main character at the final stage of the world’s consumption by the hive fleet. For that purpose they have kilometric tentacles witch could easily trap even a Ramilies star fort. A planet devourer is armed with 4 planetary feeding tentacles each one must be ‘fired’ upon any enemy ship near the Planet devourer. Every tentacle count as having feeding tentacles and massive claws, witch means it inflicts up to 3 hits to the target ship, It needs 3 hits to trap the ship using the same rules of massive claws but not halfting the strength of the Planet devourer. Every ship can try to destroy the tentacle by firing its weapons, but the tentacle counts as an attackcraft in hits purpose.
DAMAGE
A Planet devourer is not subject to frenzied quality unlike other tyranid vessels but it is subject in addition to hostile environment and stalwart due to its enormous size. It Must be considered a tyranid ship in all purposed of hit and run attacks but with a 4+save to hit and run attack due to its enormous size and it can only be boarded by defences like Space Hulks, Roks, Kroot warspeferes…
Whenever the planet devourer is hit the tyranid player ‘must’ place 3 blast markers anywhere along the Planet devourer course after each move.
CATASTROFIC DAMAGE
When the Planet devourer is reduced to 0 Hp Damage rolls on the Catastrophic Damage table. The drifting and blazing hulk results remain unchanged. A plasma drive overload result no damage is scored on ships nearby, instead the hulk breaks up into an inferno Cloud D3x5cm wide and long. On a warp drive implosion result the hulk breaks up into an inferno Cloud D3x10cm wide and long. An inferno cloud combines the effect of an asteroid field and a gas cloud, also every ship that touches the hulk base or ends in the inferno cloud will suffer 2D6 hit and run attacks as the remaining tyranids organisms will attack everything containing organic sources.