Mine a Planet Pet Fusion & Upgrade Guide: XP & Mastery

Mine a Planet pet fusion and upgrade systems let you level up pets, increase their passive bonuses, and fuse duplicate pets into higher-tier versions. The fusion system consumes two pets of the same tier to produce a single higher-tier pet, and the upgrade system consumes pet XP to increase the equipped pet's passive bonus magnitude. This guide covers both systems, the optimal investment strategy, and the pets that benefit most from upgrade investments.

For the broader pet system overview, see our Mine a Planet pets guide. For the pet tier list, see our Mine a Planet pet tier list. This principle applies broadly across all progression stages and is one of the most reliable optimization levers in the game.

Pet XP and Leveling System

Every pet has an XP bar that fills as you break ore nodes with the pet equipped. When the XP bar fills, the pet levels up and its passive bonuses increase by a small percentage. The maximum pet level is 50, and each level grants roughly +2-5% to the pet's primary passive.

The XP required to reach each level scales exponentially, which means the highest levels require significant grinding. A level 50 Astral Cat with a maxed passive bonus can reach +150% Drill Speed, which is the maximum in the game. The exact mechanics vary slightly by patch, but the underlying principle remains consistent across all player playstyles.

Pet Fusion Mechanics

The pet fusion system consumes two pets of the same tier to produce a single pet of the next higher tier. For example, two Common Eggs can be fused into one Uncommon Egg, two Uncommon Eggs into one Rare Egg, and so on. The fusion has a small chance of producing a Legendary-tier pet when fusing two Epic-tier pets.

The fusion Drill Piece cost scales with the output tier, which means fusing your way to a Legendary Egg is expensive. For most players, it is more cost-effective to buy Legendary Eggs directly from the trade market than to fuse them from lower tiers.

Best Pets to Invest Upgrades In

The optimal pets to invest upgrades in are the pets that will be in your active loadout across the longest time horizon. For end-game players, this means the Astral Cat and Cosmic Wolf, both of which will be in your loadout for hundreds of hours of gameplay.

Lower-tier pets like the Dust Bunny and Rock Mole are not worth significant XP investment because they will be replaced by higher-tier pets as you progress. Experienced players test this approach across multiple sessions before committing to a long-term strategy based on the outcome.

Pet Trade Value by Level

Pet trade value scales with pet level, and a level 50 Legendary pet can sell for 2-3x more than a stock Legendary pet. The trade value increase comes from the higher passive bonus, which makes level 50 pets more attractive to end-game buyers.

For trade-focused players, leveling pets before selling them is a meaningful Drill Piece income source. The XP investment pays for itself in the higher sale price. Combining this insight with active pet bonuses and prestige multipliers yields compounding benefits that accelerate overall progression.

Pet Collection Tips for Completionist Players

For players who want to collect every pet in the game, the optimal strategy is to farm one of each tier and fuse them strategically to fill out the collection. The rarest pets are the Legendary-tier Cosmic Wolf and Astral Cat, which require either hatching Legendary Eggs or buying from the trade market.

A complete pet collection requires roughly 30-50 hours of focused farming and fusion work, depending on luck with the Legendary hatch rates. Most completionist players accept that the Cosmic Wolf will require a trade market purchase, since the 25% Legendary hatch rate averages to 4 Legendary Eggs per Cosmic Wolf, which is roughly 4-8 hours of focused Void farming.

Fusion Math: When to Fuse vs When to Level

Pet fusion combines two pets of the same tier into a single higher-tier pet, but the fusion cost is steep enough that you should only fuse pets that you intend to use long-term. The general rule is to only fuse pets that have at least one high-tier stat roll, because fusing a common pet with no useful rolls just produces another common pet at higher tier. A pet with a high Ore Multiplier roll is worth fusing, while a pet with all mediocre rolls is better kept at its current tier or traded away.

For leveling, the math is similar: only invest XP into pets you intend to keep for 5+ rebirths. Pets that you will replace soon are a waste of XP, because the leveling cost is sunk and the bonus will be lost when you swap the pet out. For more on the long-term pet investment strategy, see our pet tier list.

Mastery Bonuses Across the Pet Collection

Each pet has a mastery bonus that unlocks when you level the pet to its maximum level. The mastery bonus is a permanent stat boost that applies to every pet in your collection, which means leveling one pet fully can indirectly buff your other pets as well. This is why high-level mastery on a few pets is more valuable than mid-level mastery on many pets.

For veterans, the optimal mastery strategy is to fully master 3-4 key pets (one +Drill Speed, one +Ore Multiplier, one +Smelt Speed, and one +Rare Drop Chance) and leave the rest at mid-level. This gives you the maximum mastery bonus across all four stat categories without spreading your XP too thin.

Frequently Asked Questions

What is the maximum pet level?

The maximum pet level is 50. Level 50 pets grant roughly +100-150% to their primary passive bonus, depending on the pet tier and stat spread. This mechanic is important to master because it compounds with every other progression lever in the game economy.

Can I fuse two different pets of the same tier?

Yes, you can fuse any two pets of the same tier, regardless of their specific type. The fusion output is a random pet from the next higher tier, so the specific pets you fuse do not affect the output. Yes, but the optimal approach depends on your current progression stage and your stockpile of supporting materials.

Should I level up pets before or after fusing?

Level up after fusing. The XP investment goes further on a higher-tier pet, and you avoid the risk of leveling up a pet that you might want to use as fusion material. Generally yes, but the optimal timing depends on your current resource reserves and your active biome's node HP profile.

Is pet fusion worth the Drill Piece cost?

For players who want to maximize their Legendary pet hatch rate, fusion can be worth it. For most players, buying Legendary Eggs directly from the trade market is more cost-effective. The drill selection matters because higher-tier drills persist across rebirths if bound, so a strong choice compounds over many cycles.

What is the best pet to invest XP in?

The Astral Cat and Cosmic Wolf are the best pets to invest XP in because they are the end-game staples that will be in your active loadout for hundreds of hours of gameplay. Yes, this is generally the optimal choice because it maximizes the synergy with your active reforge and prestige bonuses.

When to Stop Investing in Pet Upgrades

There is a soft cap on pet upgrade value beyond level 40. The XP investment from level 40 to level 50 is roughly 600,000 XP, which translates to many hours of focused grinding. The passive bonus increase from level 40 to level 50 is meaningful but not as dramatic as the increase from level 1 to level 20.

For most players, the optimal stopping point is level 40 on the Astral Cat and Cosmic Wolf. This gives you most of the passive bonus benefit without the heavy XP investment required for level 50. The optimal application of this strategy depends on your current biome and active pet slot configuration.

How to Get Pet XP Faster

Pet XP is gained passively by breaking ore nodes with the pet equipped, which means the fastest way to gain pet XP is to grind on the planet where you spend the most time. For end-game players grinding on Nebula and Void, this means pet XP accumulates naturally as part of the regular farming routine.

There is no way to directly purchase pet XP or boost the XP gain rate outside of limited-time events. Players who want to max their pets quickly should focus on extended grinding sessions on the highest-yield planets. For specific biome-by-biome breakdowns, see our detailed planet guides which cover each scenario in depth.

When to Use Pet XP Boosters

Pet XP boosters are limited-time boosts that grant 2x pet XP for a fixed duration. The developers occasionally ship these during anniversary events or pet-focused events, and the 2x boost roughly halves the time required to level a pet to 50.

The optimal time to use pet XP boosters is immediately after acquiring a Legendary pet, when you want to push it to level 50 as fast as possible. Save your XP boosters for these moments rather than spending them on lower-tier pets that you will eventually replace.

How to Roll Pet Bonuses for Maximum Effect

Pet bonuses are randomly assigned when the pet is first acquired, but they can be re-rolled using the Pet Fusion system. By fusing two duplicate pets, you can re-roll the bonus spread and potentially get a higher roll on your preferred stat. This is the only way to optimize the bonus spread beyond what you initially received.

Common Pet Fusion Mistakes to Avoid

The most common pet fusion mistake is to fuse two high-tier Legendary pets into a single Legendary pet, when a re-roll of the same pet might have been more valuable. Each fusion consumes two pets and produces one, so the fusion has to be net positive in expected value to be worthwhile.

For Legendary pets with already-good passive spreads, the expected value of fusion is often negative because the new random roll might be worse than the original. Most end-game players keep their best Legendary pets untouched and only fuse duplicates. Veteran players typically learn to recognize these patterns within the first 10-15 hours of focused play.

Pet XP Boost Sources Outside of Events

Outside of limited-time events, the only consistent pet XP source is breaking ore nodes with the pet equipped. The XP gain rate is roughly 1 XP per swing, which means a focused 1-hour farming session grants roughly 3,600 XP per pet (assuming 1 swing per second).

This rate is too slow for players who want to max their pets quickly, which is why pet XP boosters from events are so valuable. Save your XP boosters for max-level pet projects rather than spending them on early-game pets that will be replaced soon.

Pet Fusion Cost Optimization

The pet fusion Drill Piece cost scales with the output tier, with each tier costing roughly 5x the previous tier. Fusing Common to Uncommon costs 10,000 DP, Uncommon to Rare costs 50,000 DP, Rare to Epic costs 250,000 DP, and Epic to Legendary costs 1,000,000 DP.

The escalating cost means that fusing from Common to Legendary costs a total of 1,310,000 DP across four fusions, which is cheaper than buying a Legendary Egg directly. The trade market is more cost-effective for time savings, but fusion is the only way to obtain pets without spending Drill Pieces on the market.