CurseForge · Minecraft mod
O.S Pets - Evolving Companions
Eight companion pets that level to 100, evolve four times and pick one of three paths: dragons, golems, a nanite swarm, a phoenix and more.
Quick answer
Which O.S Pets - Evolving Companions release should I use?
O.S Pets - Evolving Companions OS-Pets-3.5.1forge-1.21.1.jar targets 1.21.1 with Forge. The project page does not say whether this file belongs on the client, dedicated server, or both. No extra mods listed for this file.
Where it goes
Is O.S Pets - Evolving Companions required on the client, server, or both?
The project page does not say whether this file belongs on the client, dedicated server, or both.
The source does not explicitly classify this release as client-only or server-only.
What else does O.S Pets - Evolving Companions OS-Pets-3.5.1forge-1.21.1.jar need?
OS-Pets-3.5.1forge-1.21.1.jar. Change the file and its required mods may change too.
This file does not list any required mods. Do not add a library just because a different file uses it.
This file does not list any required or optional mods.
Before you install it
Add O.S Pets - Evolving Companions without breaking your instance.
Built for O.S Pets - Evolving Companions OS-Pets-3.5.1forge-1.21.1.jar. Pick another file and the loader, install side or required mods may change.
- 01
Stick to this file
Use OS-Pets-3.5.1forge-1.21.1.jar. It targets 1.21.1 with Forge; another release may have different loader, side or dependency requirements.
- 02
Bring the mods it needs
This file does not list any required mods. Do not add a library just because a different file uses it.
- 03
Put it on the correct side
The project page does not say whether this file belongs on the client, dedicated server, or both.
- 04
Pick the file you checked
Use the “Get this file” button beside OS-Pets-3.5.1forge-1.21.1.jar. It opens that exact file at the source.
About this project
What does O.S Pets - Evolving Companions add?
[O.S] Pets
A companion that grows with you for the whole game. Pick one of eight pets, level it from 1 to 100, watch it evolve four times and choose one of three development paths. Every path has its own look, abilities and ultimate. Your pet fights next to you, carries your loot, heals, farms and mines, and it can never be lost.
Getting started

- When you first join, the chat offers you a pet. You can also press P and pick one in the pet window.
- Your pet appears next to you. It follows you, attacks whatever attacks you and picks up loot.
- Kill mobs, mine and collect experience together. Every XP orb you pick up also gives your pet XP.
- Every level gives a skill point. Every 25 levels the pet evolves.
- At level 25 choose a path. At level 75 the ultimate opens: press G.
You can change your pet's body at any time. Level, skills and bag are kept. If anything is unclear, open the Pet Handbook (book + bone): it has a page for every pet with a live 3D preview of all its looks.
The pets
| Pet | Role | Special |
|---|---|---|
| Dragon | Fighter | Breathes fire from evolution II, becomes a flying mount at level 100 |
| Golem | Tank | Pulls mobs off you onto itself, punches launch enemies |
| Nanite Swarm | Fighter | A cloud of bots that forms a blade, shield, drill or a giant |
| Crystal Turtle | Protector, mount | Rideable from level 25, swims under water, later carries two players |
| Auralis | Fairy healer | Removes debuffs, heals, gives buffs to everyone nearby |
| Pollenkin | Farmer | Speeds up crops, harvests and replants on its own |
| Phoenix | Fiery flyer | Sets enemies on fire, is reborn after death |
| Living Armor | Bodyguard | Takes 35-60% of the damage aimed at you |
Small pets can sit on your shoulder: the dragon (up to evolution II), the phoenix (up to III) and Auralis. The pollenkin sits on your head.
Three paths for every pet

At level 25 your pet chooses one of three paths. Each path changes the look at every stage, the stats, the passives, the attacks and the ultimate. Changed your mind? A Rebirth Crystal resets the path. Level, skills and bag stay.
| Pet | Path | Ultimate |
|---|---|---|
| Dragon | Fire: fire breath, immune to lava | Wall of Fire |
| Whirlwind: faster flight, water jet instead of fire | Tornado | |
| Storm: chain lightning that stuns | Thunderstrike | |
| Golem | Crystal Guardian: reflects arrows, thorns | Crystal Prison |
| Magma Brute: burning fists, fire waves | Eruption | |
| Brass Engine: mines whole ore veins into its bag | Overdrive | |
| Nanite Swarm | Assault: executes weak enemies | Blade Storm |
| Engineer: stronger shield, repairs your gear | Guardian | |
| Parasite: poisons and weakens on every hit | Subjugation (enemies fight for you) | |
| Crystal Turtle | Crystal Fortress: tough, hurts attackers | Crystal Dome |
| Tidal: fast in water, heals you in rain | Tsunami | |
| Volcanic: walks on lava, fireproof rider | Lava Bombs | |
| Auralis | Healer: heals you when you are low | Blessing |
| Enchantress: curses enemies | Charm (enemies fight each other) | |
| Starlight: star beams, night vision | Starfall | |
| Pollenkin | Gardener: bigger and faster farming | Bloom |
| Briar: poison pollen, slowing vines | Toxic Bloom | |
| Hive: its own bees, brings honey | Swarm | |
| Phoenix | Flame: more fire | Firestorm |
| Solar: heals players, saves you from one death | Rebirth | |
| Frost: ice feathers that slow and freeze | Ice Storm | |
| Living Armor | Paladin: bigger shield, taunts | Merge (wraps around you) |
| Berserker: greatsword, lifesteal | Blade Whirl | |
| Phantom Knight: teleports, throws blades | Army of Shadows |
Evolutions



At levels 25, 50, 75 and 100 the pet evolves. It gets new body parts, glow and abilities, and its health and damage grow. The dragon, golem and turtle also grow a lot in size: the dragon goes from a tiny hatchling to a two-block dragon you can fly. Every pet has 21 looks: five base stages, a mythic form and five stages for each of its three paths.
Nanite Swarm

The swarm is not one creature but dozens of tiny bots. They float around your shoulder as a cloud, form a blade in combat, flash into a shield when you are hit, turn into a drill while you mine, build a giant Guardian as their ultimate and spread into a radar ring when scouting.
Mythic forms

At level 100, right-click your pet with a Mythic Heart to awaken its mythic form: x1.25 health and damage, +6 armor and a new look for its path. The Mythic Heart is an endgame recipe: a nether star, 2 totems of undying, 4 echo shards and 2 dragon's breath.
Skills and modes
Skills. One point per level, up to 50 per branch. Resetting is free.
| Skill | What it gives |
|---|---|
| Attack | +1.5% damage per point |
| Defense | Health, armor and knockback resistance |
| Support | The pet heals you and heals itself faster |
| Utility | Bigger pickup range and speed |
Modes.
| Mode | What the pet does |
|---|---|
| Follow | Follows and protects you |
| Guard | Attacks every hostile mob around you on its own |
| Mine | Stays close and collects loot from further away |
| Farm | Stays on its field, harvests and replants crops |
| Scout | Highlights enemies around you and avoids fights |
Smart behaviour
- Real tanks. The golem, the Paladin armor and the Crystal Fortress turtle pull mobs off you and hold their attention.
- Own flight style. The dragon glides and dives, the nanites dart around and engulf targets, the phoenix circles and makes strafing runs, and the fairy hides behind you.
- Fair against bosses. Pets deal only 35% damage to bosses and to any mob with 150+ health. They clear ordinary mobs fast, but bosses are still yours to beat.
- Never in the way. Pets don't push players and never hurt their owner. They back off from creepers and don't attack villagers, iron golems or other players' pets.
- Never lost. A pet is stored with the player, not in the world. It comes back when you join, change dimension, or 30 seconds after it falls.
Equipment
Three slots: collar, amulet and charm. Each has 2 kinds × 4 tiers, 24 items in total. Each tier needs a pet level of 25 / 50 / 75 / 100 and is crafted from the tier below. A full tier IV set takes several nether stars and dragon fights, so a fresh pet can't be made overpowered.
| Item | Effect |
|---|---|
| Collar of the Guardian | More health and armor |
| Collar of the Wind | More speed, faster respawn, wider pickup |
| Amulet of Fury | More damage |
| Amulet of the Sage | Ultimate more often, more pet XP |
| Charm of the Vampire | Lifesteal |
| Charm of Life | Regeneration, heals you every 5 s |
Right-click your pet with a piece to put it on. Click its slot in the pet window to take it off.
Interface
- Pet window (P) with tabs: overview with a 3D portrait, path, skills, mode, settings and the handbook.
- On-screen panel with portrait, health, XP, target and ultimate cooldown. You can turn it off in the settings.
- Keys: P pet window, G ultimate, B attack the mob you look at, N call the pet back. All keys can be changed.
- Own sounds for every pet: voice, hurt, death and ultimate.
- Fully translated into English and Russian.
Items
| Item | What it does | How to get it |
|---|---|---|
| Pet Handbook | Opens the illustrated guide | Craft: book + bone |
| Rebirth Crystal | Resets the development path | Craft: 4 amethyst shards, 4 gold ingots, a diamond |
| Mythic Heart | Mythic form at level 100 | Craft: nether star, 2 totems of undying, 4 echo shards, 2 dragon's breath |
| Collars, amulets, charms | Pet equipment, 4 tiers | Tier I from its own materials and a diamond, every next tier from the previous one |
For servers and modpacks
- Operator command
/pet xp <amount> [players]gives pet XP, handy as a quest reward. - Player commands:
/pet info,/pet summon,/pet dismiss,/pet choose,/pet branch,/pet name,/pet skill,/pet respec,/pet mode,/pet ultimate,/pet recall,/pet hud,/pet sounds,/pet shoulder. - Works on dedicated servers. Install it on both the client and the server.
- Needs only NeoForge 1.21.1.
Works with other O.S mods
All of these are optional. Pets works fine on its own.
- [O.S] Industrial: the Industrial Colossus boss drops the Heart of the Colossus, which also awakens the mythic form. When Industrial is installed, the Mythic Heart recipe is turned off.
More O.S mods:
- O.S Pets - Evolving Companions - Eight companion pets that level to 100, evolve four times and pick one of three paths: dragons, golems, a nanite swarm, a phoenix and more.
- O.S Utilities - All-in-One QoL - Right-click harvest, double doors, quick deposit, inventory sorting, coords HUD, dynamic light, auto-refill and more.
- O.S Engineering - Quarry & Transport Pipes - A FE-powered Engineering Quarry (16/32/64) and classic transport pipes: 11 item pipes with sorting, extraction and suction, plus fluid pipes.
- O.S Races and Classes - 10 races, 10 classes, constellation-style skill trees (PoE inspired).
- O.S Elites - Monster Affixes
- O.S Dungeons - Bosses & Trials
- O.S Loot - Rarities & Affixes
Discover more projects from O.S and follow future updates.
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Project description from CurseForge.
Pick your setup
O.S Pets - Evolving Companions by Minecraft version and loader
Choose the version and loader you play, then open the matching release.
1.20.1
2 loader buildsCheck the dependencies, then try the file in a copied instance before changing a world you care about.
Recent files
O.S Pets - Evolving Companions versions and loaders
OS-Pets-3.5.1forge-1.21.1.jar
26 Oct 2026
OS-Pets-3.5.1forge-1.20.1.jar
26 Oct 2026
OS-Pets-3.5.1fabric-1.21.1.jar
26 Oct 2026
OS-Pets-3.5.1fabric-1.20.1.jar
26 Oct 2026
OS-Pets-3.5.1.jar
ObmorokPets-3.5.1.jar
18 Oct 2026
Looking for an older file? The official CurseForge project page is in Resources.