I have a Artifice-Godbound that wants to use his Dominion points to create siege weapons. How would you stat up something like that?
Should I model it like a weapon for mobs? Its own mob? Or perhaps an automaton/creature?
You can use Dominion to create a single, Artifact siege weapon. Alternatively, you could use it to create a Fact along the line of "GROUP is well-equipped with siege weapons and engineers," if the objective is to actually use armies to wage seige warfare.
If you're using the Factions rules: I would definitely use it as a feature for the attackers, as
has mentioned—I disagree in regards to making a siege weapon as an artefact, unless the goal is to simply eradicate the entire city.
As a mundane weapon, if you're using it as such (I am working under the assumption that it is a ranged weapon): I would make it a weapon which must be moved very slowly, deal 3d8 (modified by Intelligence) damage die to a very small area of space, and deal maximum damage to objects in the area.
Are you talking about spending Dominion to equip an entire city/nation? Magical siege engines? Is it for one use or as a long term item?
If it was not magical and was for a single siege, I would let them use influence or actually just build the things themselves.
If it was to fortify something long term, I wouldn't make it any more costly than equipping the same area with swords since everyone in the city or military isn't getting one.
Stat wise, if you have to figure damage, I would allow it to do 1d10, or 1d12 at most, applied straight to mobs. Maybe inflicting something special like burning or disease depending on ammo.
I don't think you would want to let a non magical item do more with a hit than a person with the Might word can.