This Solar Auxilia Basilisk was on display at Warhammer World.
Many Solar Auxilia Cohorts maintain their own mobile artillery batteries, favouring a class ideally suited to their particular battle doctrines.
Firing from long distance, the Basilisk can lay down a fearsome barrage ahead of the advancing ranks of the Solar Auxilia. Their hulls, derived from the Solar pattern Leman Russ, offer enhanced protection from enemy weapons and can equip a pintle-mounted weapon such as the ubiquitous multi-laser, adding a close quarters defence capability should enemy infantry advance too near.
I think that Games Workshop missed the target with the Vostroyans, they had an opportunity to make something as good as Forge World’s Death Korps and I believe that they missed the boat. The Vostroyans are not quite right in my opinion, though I know others like them.