I’ve seen a lot of posts about taming creatures, but the majority of them have either been designed around either riding/fighting with, or as a way to farm bone and meat. My suggestion is that we have a unique purpose to domesticating creatures. These purposes with scale with tier and would be unique to the world.
Wildstock
Wildstock are domesticated for their milk. Milk is already in game and is useful for crafting foods, but domesticated Wildstock would allow for milk to be gathered without killing the creature once a game day with a bucket. A machine would be craftable that would allow for auto milking so you can travel and not miss your milkings, but it would have the ability to wear out.
Beyond simple milk, Wildstock happen to consume a large amount of inorganic material in their wanton grazing, especially higher tier creatures. This means that their milk will contain trace amounts of minerals. This milk can be processed to isolate the mineral contents and returns ores of varying types.
At the highest tier, this milk could even contain trace amounts of roughly gems native to the planet!
In practice, we’d be able to use an extractor to process large amounts of milk (I’m thinking like 30 at base) in to ore. Each tier creature would would return a tier of ore; Iron, silver, gold, titanium, gem. The milk could even be tinted for ease of storage.
Spitter
Spitters can be tamed as highly effective guards. Harassing would be trespassers as well as invasive mobs. Such smart creatures, Spitters would even gather drops from creatures they kill and store them in nests for you to collect later. Of course they eat the meat themselves.
Spitters are wondrous creatures capable of creating a nearly endless supply of their ammo. Higher tier Spitters can even create bombs that look manufactured!
Misunderstood and unappreciated, the poor Spitter actually needs to get rid of the stones it creates or they can cause uncomfortable backups. By creating a dummy target machine for your tamed Spitter, you can both ensure it has a way to get rid of eccess ammo, and conviently collect these resources for yourself!
These resources would largely be components for thrower augments and for making unique bombs. This would need to be fleshed out more, but I imagine the highest tier would produce elemental shards. Maybe you need to have tamed elemental Spitters to get shards. Open to feedback on that one!
Cuttletrunks
Energetic creatures, Cuttletrunks need a lot of open air to roam, but when domesticated, can provide effective air support for your Spitter guards. However, these creatures are more than just muscle though. The organs that allow them to float and fire blasts of energy, can also be utilized to provide power to your machines, your portals, or even to produce gleam.
Grounding rods can be constructed that will allow your lower tier Cuttletrunks to discharge spark. When connected to a spark core, this spark can be stored. Alternatively, these can be connected to portal conduits to provide more time active. High tier Cuttletrunks can do this, and will also deposit gleam appropriate to the planet.
I imagine this spark/portal power production would scale up by tier. Tier 1 Cuttletrunks would produce 100 spark per game day, with top tier producing 1000 spark. For portals, I think each tier could produce a scaling amount of time to connected portals. Between 1 hour to 1 day of portal time a day. This gets split between all the portals you have connected to your rod.
If you have high tier Cuttletrunks, gleam would randomly build up around the grounding rod at a slow rate. I’m not sure if this should be a unique gleam color, or the color of the gleam on the planet.
I’m not sure yet about hoppers and roadrunner. But I’ll update this if I have an idea!