Creating your own machines
Keep in mind a few simple guideline questions when creating your own machine.
Which AI designed it?
DEMETER-designed machines perform some ecological role and mirror an animal species likely to be reintroduced in the future. HEPHAESTUS-designed machines perform labor roles and are generally not intended to be seen above ground or interacting with humans, and therefore have a utilitarian, non-animal aesthetic. Human-designed machines, predating Zero Dawn, only survived if they were part of the military swarm.
What is its function?
Most machines are created with one, sometimes two, intended uses. Striders work the land, while Shell-Walkers provide over-land resource transport. Even Stormbirds, as weaponized as they have become, were originally designed to seed rainclouds and provide air transport.
What is its form?
This should logically follow its function. For example, a machine designed to pick fruit from tall trees and spread seeds might take the form of an orangutan. A machine designed to seed river systems with algaes and bottom-feeding crustaceans might take the form of a ray or an octopus.
If an AI other than DEMETER influenced the design, it should be reflected in the form. HADES-influenced machines may still perform their intended role, but will likely also be larger, have more armaments, and be more aggressive than normal. HEPHAESTUS-influenced machines might be bulkier and less graceful, and have more anachronistic features such as anti-grav plates instead of legs.
What are its defenses?
Even an “unarmed” machine like the Watcher can defend itself, whether with its feet, its tail, or even just using itself as a projectile. More aggressive machines might have teeth, claws, horns, and other physical traits which can be used as weapons, even if they don’t have explicit armaments.
Consider also how tools which befit the machine’s function might be repurposed as weapons. Bellowback flame throwers might have been designed to start controlled fires, while the Shell-Walker’s electric bolts might have started as arc welding tools. Even the Corruptor has non-obvious weapon options: it can use its scorpion-stinger arm to fling rocks and other objects, making improvised missiles.
What are its weaknesses?
Every optimization for one purpose should yield a design compromise, and therefore a weakness. Deathbringers may have nigh-unlimited ammunition and ridiculous armor, but all that weight limits their mobility and all that armor means they have to occasionally expose vulnerable heat sinks to open air. Snapmaws have significant armor plating, but those plates are vulnerable to being shot or blown off, leaving exposed weak spots. Ravagers have cannons which can do significant ranged damage, but those cannons can be destroyed.
Consider the destructible parts of your machine: define what can be disabled, detached, or destroyed, and how that affects both the machine’s behavior and the party strategy. This destruction does not always have to work in the party’s favor. For example, a control module might limit a machine’s strength as a safety measure around humans, so destroying it might make the machine’s attacks even stronger.
What are its limitations?
Invincible enemies with unlimited range and ammunition aren’t fun. A Stormbird that only shot lightning balls from a thousand feet in the air would make for a grueling fight, as would a Bellowback which produced an impenetrable, unending ring of fire. In fantasy settings, this is why dragons have to wait or roll to get their elemental breath attack back.
Try to come up with limitations in the tactics of your machine to encourage coordination or planning in your players. Stormbird bolts have limited range, along with capacitors which take time to recharge after each shot, requiring it to fly down into melee range to attack. Bellowback snouts run the risk of overheating or freezing solid, so they need to regularly pause their ranged attacks to let their snouts cool or thaw. Stalkers are built for stealth and agility, limiting their options for armor and weapons.