Earthbounds

Pertilyo

Pertilyo is a bat-like Earthen made of Copper and Cobwebs. The only place it can be found is in Dripstone Caves, beneath the Deepslate layer of your world.
It is completely neutral, as it will ignore anyone's presence and just go about its day. If there is one thing though that the Pertilyo hates, is torches. When this blind fellow senses a torch, it will fly towards it and proceed with its absorption. Once the torch is absorbed, the copper Earthen will begin producing excess Glow Grease, until it plops it out and drops onto the ground.

You may want to be careful when you travel around Dripstone Caves, since as little as two Pertilyos can quickly get rid of any torches you placed and create a perfect habitat for hostile creatures.

As this lil guy is made of Copper, it can oxidize. Oxidized Pertilyos tend to roost on ceilings more often than its fresh peers, and tend to behave quite strangely when there's a thunderstorm. They will frantically attempt going above ground, to try cleansing themselves of the oxidation. Once they do get above ground, they'll shut down and wait for a lightning to strike them to de-oxidize. Why does this matter to you? Well, if the Pertilyo gets struck by lightning while in its oxidation phase, it will drop a Pertilyo Rod.

Pertilyo Rod

The Pertilyo Rod is a rare item which can be two ways: Either by witnessing a Pertilyo's de-oxidation process, or through crafting with the use of 3 Pertilyo Fragments. These can be found both as a treasure in Abandoned Mineshafts and as a rare drop from Pertilyos. Once the Pertilyo Rod is crafted or obtained, you can craft The Flingshot.

The Flingshot + Shimmer Shell

The Flingshot is a versatile weapon which is created using two copper ingots, two strings, a rabbit hide, an amethyst and a rare Pertilyo Rod. There is a wide selection of ammo it may use, the current list including Glow Grease, Shimmer Shells and Flinging Potions. To use a Flingshot, hold it in your preferred hand and hold your desired ammo in your other hand. A Flingshot may be repaired at an Anvil using Copper Ingots.
Shimmer Shells are the most valuable ammo Flingshots may use: they are small explosive shells, which go off shortly after touching the ground. These are particularly effective against Earthen creatures.

Copper Bucks, Madder Bucks

Copper Bucks and Madder Bucks are two other types of ammo designed for the Flingshot.
The Copper Buck is a simple damaging Buck, effective against Earthen mobs. With a bit of luck, these can bounce off multiple creatures and deal a hefty amount of damage.
The Madder Buck is a small shell that upon impact, sprays mobs in an area with the "Rubia" effect. You can read more about it in the "Fossilized Rubro" section.

Flinging Potions

Flinging potions are potions which can be flung using a Flingshot. They behave similarly to Throwing Potions, and they are made by adding Amethyst Dust to a brewed potion.

Enchantments

The Flingshot has four unique enchantments which can be found:
- Precision (I-V): Improves the Flingshot's Accuracy
- Force (I-III): Makes the Flingshot's shots travel further
- Automation: Makes the Flingshot shoot automatically when fully drawn
- Versatility: Allows the Flingshot to fling item drops

Glow Grease

When exploring Dripstone Caves, you may come across splashes of Glow Grease. This is a special type of block, which makes any surface slippery. It also has an additional property: it emits light! 
Finding these usually means a Pertilyo was or is nearby.

Fun fact: Amethyst dust can be used or put in a dispenser to create a cloud of shiny particles!

Rubro

Rubro is a neutral feline-like Earthen made of Redstone and Stone/Deepslate. It can sometimes be found near Redstone Ore veins and deposits underground.

Rubros tend to look for Redstone Ore to scrape with their claws, in order to charge themselves. Charged Rubros develop an innate sense of smell, meaning they will kill any foreign creature that's not made of Redstone. Additionally, they can tell if you've recently mined Redstone, meaning that no matter what you do they will try taking it off you through their hostility.

A hostile Rubro will quickly pounce at you, followed by them hitting you where your shield can't reach with its tail (They tend to aim at your feet - this means you might be able to avoid this attack by jumping at the right time). 

Rubros are completely neutral to players who are holding Redstone in either hand. Think of it as some "sign of peace", which however is broken if you even dare touching their precious ore.

Bottled Rubia

Lastly, right-clicking on a Powered up Rubro with a glass bottle allows to collect its rage and power, filling the container with Rubia.
Bottled Rubia can be tossed like a Bottle o' Enchanting, and any entity hit by the contents will attract Rubros and Fossilized Rubros attention.

Fun fact: Rubros despise witches! They can't stand the waste of Redstone they go through when making potions.

Though a Fossilized Rubro does not spontaneously attack things, it will become extremely aggressive towards anything with the new Rubia effect. Additionally though, Rubros are passive unless charged with Redstone (similarly to how normal Rubros behave). These little guys are powerful, and take 60% reduced damage from most sources.

Fossilized Rubros come in 12 variants, 6 being Stone variants and 6 being Deepslate variants.

Redstone Fossils

Redstone Fossils are new rare ore that can be found underground, at roughly the same depth as Redstone. When these are broken, they drop both their corresponding mineral (Gilded Redstone Fossil will drop Raw Gold for example), and Primordial Redstone.
Primordial Redstone is a new, powerless and ancient variant to Redstone that Rubros go crazy for. It can be used both to heavily power up a Rubro, and to heal it in case its withstood heavy damage. 
Default Redstone and Deepslate Redstone Fossils are common, while all other variants are 5 times more rare. Good luck finding your favorite one underground! And also, make sure to keep a Crumble III pickaxe with you to break the Fossil for a surprise ;).

Helpful tip: Fossils make creaking sounds when placed. You can use these creeks to help yourself finding them.

Rubia

Earthbounds has an included Origins addon which adds a new Origin: Rubian!
It's an advanced Origin which can be very effective at exploring caves and in PvP. You can read more about it HERE

Q: I found a weird ore underground which just drops itself... What's that about?
A: That... You will find out soon ;)

Q: Rubros keep killing me any time I reach the Deepslate layer of the world... What should I do?
A: Rubros do not like other beings that dig Redstone or who smell like.. themselves. Hold some Redstone in your hand and you will probably be fine... Just hope that they don't notice if you mined Redstone Ore in the past 5 minutes or so :/

Q: Why can't I block Rubro's attacks with a shield?
A: You can only block a Rubro's pounce. Its "spin attack" can be avoided by jumping when their tail is about to hit you.

Q: Why isn't the Carboranea I found producing any coal chunks?
A: It probably means its environment is not warm enough. Provide it with heat-providing blocks and it will begin heating up. Keep in mind though that in colder biomes, the Carboranea will take longer to reach critical temperatures!

Q: Does Earthbounds work in multiplayer?
A: Yeah, the mod works great in multiplayer.

Q: Can you make a <1.18 version?
A: No. That would require a LOT of time and effort since I am alone developing the mod. I'd rather focus on expanding the mod further for the current version.

Q: ...Forge?
A: Maybe. Once this update has become stable, I will start a mod rewrite in MojMaps, which will bring us one step closer to a Forge release.

Q: Can I include Earthbounds in X modpack?
A: Of course! Make sure though to credit me, similarly to how you'd credit other mod creators in the modpack.

Q: Can I make a video on Earthbounds?
A: Yup, make sure to credit the author (me) appropriately though! And maybe shoot me a DM with the link so I can take a look :)