Oofta
Legend
The way I would approach it would be to look at existing monsters (such as empyrians) but then do some high level guessing on PC class equivalency.
Assuming that you want these devices to be used by PCs, how big of a character multiplier do you want this to be? In other words if two PCs are required to run the mech, how much more powerful are they than if they didn't have the mech?
So if you want the mech to be 4 times as powerful as a standard PC, then it should have 4-5 times the damage potential and roughly 4-5 times the hit points. You want to up the numbers a little bit because a single target is easier to focus on for most opponents and damage is going to be a little more concentrated.
Take a look at your group or take a quick swag at how much a barbarian of the appropriate level would do on average. For melee attacks target total damage for a round based on what 4 barbarians could do. This may be spread out on multiple targets - I can see a mech having any number of close area effects.
Decide what spells you want to mimic. I'd stick with standards like fireball, lightning bolt and so on. A mech should be big and flashy.
Change the flavor of the spells as you see appropriate - a meteor swarm is a great stand-in for an artillery strike for example.
Make sure all spell-like attacks are limited in number (similar to a caster of the appropriate level). You can either up the damage, spread it out or just give the mech multiple shots. A gatling-lightning-bolt could shoot up to 4 lightning bolts for example. Justify need for short/long rests as needing to refuel/repair.
Base number of spells on appropriate level wizard/sorcerer.
So that's it for offensive. Defenses are a little tougher, but I'd do something like give the passengers immunity to damage for a while until their mech is 50% damaged, then it goes to resistance. If the mech is on it's last legs, panels have fallen off, sparks are flying and the mech may be doing bad things to the drivers.
By doing all of that, the mech now counts as 4 PCs and your encounter challenge ratings shouldn't be too difficult, although you are going to effectively have a large group which does throw off some calculations.
A last note though - you need to be sure both people have enough to do. It might be kind of boring to be the guy "steering" the mech. Make sure they have enough to do.
Overall I like the idea - I may have to steal it at some point!
Assuming that you want these devices to be used by PCs, how big of a character multiplier do you want this to be? In other words if two PCs are required to run the mech, how much more powerful are they than if they didn't have the mech?
So if you want the mech to be 4 times as powerful as a standard PC, then it should have 4-5 times the damage potential and roughly 4-5 times the hit points. You want to up the numbers a little bit because a single target is easier to focus on for most opponents and damage is going to be a little more concentrated.
Take a look at your group or take a quick swag at how much a barbarian of the appropriate level would do on average. For melee attacks target total damage for a round based on what 4 barbarians could do. This may be spread out on multiple targets - I can see a mech having any number of close area effects.
Decide what spells you want to mimic. I'd stick with standards like fireball, lightning bolt and so on. A mech should be big and flashy.
Change the flavor of the spells as you see appropriate - a meteor swarm is a great stand-in for an artillery strike for example.Make sure all spell-like attacks are limited in number (similar to a caster of the appropriate level). You can either up the damage, spread it out or just give the mech multiple shots. A gatling-lightning-bolt could shoot up to 4 lightning bolts for example. Justify need for short/long rests as needing to refuel/repair.
Base number of spells on appropriate level wizard/sorcerer.
So that's it for offensive. Defenses are a little tougher, but I'd do something like give the passengers immunity to damage for a while until their mech is 50% damaged, then it goes to resistance. If the mech is on it's last legs, panels have fallen off, sparks are flying and the mech may be doing bad things to the drivers.
By doing all of that, the mech now counts as 4 PCs and your encounter challenge ratings shouldn't be too difficult, although you are going to effectively have a large group which does throw off some calculations.
A last note though - you need to be sure both people have enough to do. It might be kind of boring to be the guy "steering" the mech. Make sure they have enough to do.
Overall I like the idea - I may have to steal it at some point!
