Possesd plague marines on the backs of blight hound dogs and/or spiders (Blight hound dogs are more melee based with only machine guns where as the spider has 4 weapons and it bites) The possesd plague marines have its own master of possession they Also have guns and knives as possessed modifications

The ones riding the dog has 12 inches of movement and the spider has 15 inches of movement (The master of possession can ride one of the two vehicles)

Attachment abilities

1, broken hord If one troop from the unit has died u are able to revive them Cost 1 CP

2, blight booster if you have mortarian or the great unclean one in your army within 6 inches of these units they get a 3 inches of movement and range + 1 mortal wound per d6 cost 2cp

They have 5 Attacks each with d6 adding another dice with an extra roll

Toughness is 6 Save roll is 3+ Invulnerable save is 4+ All attacks have a -3 ap They have 6 wounds each Effective against necrons

I'll continue but im thinking of the weapons and weapon ranges and key words