PolishedDex Logo

Search PolishedDex

Search for Pokémon, moves, items, locations, and abilities

Breeding

This guide covers IVs, natures, egg moves, and competitive strategies

Introduction

Breeding produces eggs at Day Care. You control IV inheritance, natures, abilities, and egg moves. It's how you optimize competitive teams, hunt shinies (Masuda method), and get moves outside normal learnsets.

Who This Guide Is For

This guide is for players who want to:

  • Build competitive or battle ready Pokémon
  • Breed Hidden Abilities and egg moves efficiently
  • Optimize IVs, natures, and shiny odds without wasted time

If you’re just dropping Pokémon off at Day Care and hoping for the best, you’ll miss most of what Polished Crystal’s breeding system offers.

What's New in Polished Crystal

Polished Crystal changes:

  • Mirror Herb – Transfer egg moves between parents at Day Care[1]
  • Ability Capsule/Patch – 25% chance per parent to pass Hidden Ability[2]
  • Mr. PKMN's 6IV Shiny Ditto – Trade Red Scale for perfect breeding stock[3]
  • Nidorina/Nidoqueen breedable – Now in Monster/Field groups (vanilla had them in Undiscovered)[4]
  • Form inheritance – 50/50 when same-species parents have different forms[5]
  • Pokéball inheritance – Offspring will inherit the mother/non-Ditto's ball. If both parents share the same species, offspring can inherit ball from either parent[5]

Breeding Compatibility Tool

Instead of memorizing egg groups, use the interactive compatibility checker below. It shows every Pokémon that can breed with your selected species, grouped by shared egg group - ideal for planning egg moves and breeding chains.

Loading Pokemon data...

Egg Groups

Egg groups determine breeding compatibility. Two Pokémon breed if they share at least one group (except Undiscovered). Offspring species comes from the female parent (or non-Ditto parent when breeding with Ditto).[6]

Most players won’t need to memorize egg groups. Instead, focus on Pokémon that belong to multiple groups, since they act as bridges for egg move transfer. Marill is a common early-game example that can connect Fairy and Water 1 breeding chains.

Polished Crystal uses 15 egg groups:

Pokémon in multiple groups act as breeding bridges. Marill (Water 1 + Fairy) can transfer egg moves between those groups.

Gender Ratios

Gender ratios affect breeding efficiency since offspring species comes from the female parent (or non-Ditto parent).

Egg Move Inheritance

Egg moves are moves only accessible through breeding. Male parent moves transfer first, then female moves. The move must be in the offspring's egg move pool.[7]

Key rules to know:

  • Male parent moves take priority
  • Move must exist in offspring's egg move pool
  • Offspring hatch with inherited moves already learned
  • Multiple egg moves transfer when both parents have moves in the pool

Mirror Herb

Mirror Herb transfers egg moves between Pokémon at Day Care:[1]

  • Ensure there are empty move slots on the Pokémon you want to inherit a move. You can delete moves using the Move Deleter in Blackthorn City
  • Give this pokemon the Mirror Herb to hold. You can purchase a Mirror Herb in Goldenrod Harbor
  • Get any other Pokemon that knows the egg move you want to inherit, irrespective of egg group or gender, and place both in the daycare together
  • Each step has 1/256 chance to copy an egg move to the Mirror Herb holder

Chain breeding is sometimes still needed. If Pokémon A knows a move but can't breed with Pokémon B, breed A with C (which shares groups with both), then breed C with B. Mirror Herb usually eliminates this.

Hatch Cycles and Steps

Eggs hatch after a certain number of cycles. Each cycle is ~256 steps.[8]

Faster hatching:

Ditto Breeding

Ditto is especially valuable for breeding with the following categories of Pokémon:[11]

Non-Ditto parent determines offspring species.

Find Ditto on Route 35 or Cerulean Cave postgame.[12] The only Ditto you should really be using for breeding is Mr. PKMN's perfect shiny one (see below).

Mr. PKMN's Perfect Shiny Ditto

Mr. PKMN trades Red Scale for 6IV Shiny Ditto:

  • 31 IVs in all stats (perfect for breeding)
  • Different OTID activates Masuda method (higher shiny odds)
  • Get Red Scale from catching or defeating Red Gyarados at Lake of Rage

Day Care Locations

Day Care is in Goldenrod City's south side. Route 34 below it is good for hatching.

Compatibility messages:

  • "They seem to get along very well!" – Same species, different OTs (fastest eggs)
  • "They seem to get along." – Same species same OT, or different species different OT
  • "They don't seem to like each other." – Different species, same OT (slow eggs)
  • "They prefer to play with other Pokémon." – Incompatible (no eggs)

When to Start Breeding

Early game breeding is mostly useful for:

  • Egg moves you can’t get otherwise
  • Trying to get a Hidden Ability
  • Nature control via Everstone

Full competitive breeding is best saved until:

  • You have access to Mr. PKMN's Perfect Shiny Ditto
  • You can get Destiny Knot and Everstone
  • You catch Flame Body Pokémon (Okay this is optional, but it speeds up hatching a lot)

Competitive Breeding

Battle-ready Pokémon need specific IVs, natures, and abilities.

Competitive Breeding at a Glance

  1. Choose Hidden Ability → Ability Patch/Capsule
  2. Choose IVs → Destiny Knot + 6IV Ditto
  3. Add egg moves → Mirror Herb or chain breeding
  4. Choose nature → Everstone
  5. Hatch efficiently → Flame Body + Oval Charm

IV Inheritance

IVs (Individual Values) range 0–31 per stat. Higher = better stats at level 100.

Extra Math: Polished build IVs just range from 0-15, with the IV being equivalent to a modern game IV after doing a x2+1 calculation, e.g. a Polished IV of 14 = 29 in modern (14x2=28+1=29)

How IVs pass down:[13]

  • Default: Three random IVs from parents
  • Destiny Knot: Five IVs from parents (one still random)
  • Power items (Power Weight, Power Bracer, etc.): Guarantees specific stat IV from holder

Method:

  1. Get parents with good IVs (or use Mr. PKMN's 6IV Ditto)
  2. Give one Destiny Knot
  3. Breed until offspring has better IVs
  4. Replace parent with better offspring
  5. Repeat

Nature Inheritance

Natures give +10% to one stat, -10% to another.

Common competitive natures:

  • Adamant (+Attack, -Sp. Atk): Physical attackers
  • Jolly (+Speed, -Sp. Atk): Fast physical attackers
  • Modest (+Sp. Atk, -Attack): Special attackers
  • Timid (+Speed, -Attack): Fast special attackers
  • Bold (+Defense, -Attack): Physical walls
  • Calm (+Sp. Def, -Attack): Special walls

Passing nature: Everstone on parent = 100% nature inheritance.[14]

Catch wild Pokémon with Synchronize (Abra from Goldenrod Game Corner) to get specific natures easier.

Ability Inheritance

Ability Capsule/ Ability Patch on parent: - 25% chance for Hidden Ability offspring - 50% if both parents hold one[2][15]

Female (or non-Ditto) parent:

  • 60% chance to pass its current ability[15] Get Hidden Abilities from Wonder Trade (33% chance) or wild encounters (5% chance).

Form Inheritance

Same-species parents with different forms: 50/50 chance for each form.

Different species: Female (or non-Ditto) parent's form.[5]

Everstone only affects nature, not form.

Pokéball Inheritance

Same species: Either parent's ball (50/50).

Different species: Female (or non-Ditto) parent's ball.[5]

Shiny Breeding - Masuda Method

Masuda method increases shiny odds through different OTIDs (Original Trainer IDs).[16]

In Polished Crystal:

  • Needs different OTIDs, not different languages
  • Mr. PKMN's Shiny Ditto has different OTID = auto-activates method[3]
  • Much higher shiny chance than normal breeding/wild encounters[16]
  • Stacks with Shiny Charm[17]
  • Parent shininess doesn't affect offspring IVs[16]

Optimized Breeding Workflow

  1. Get Mr. PKMN's 6IV Shiny Ditto (trade Red Scale from Red Gyarados)
  2. Get the ability you want on the parent, due to the >60% ability inheritance for offspring. Use an Ability Capsule/Ability Patch, or have a parent hold these items to increase the chance for offspring to have their Hidden Ability (25% chance per parent)
  3. Catch Synchronize Pokémon for each nature you need (Abra at Goldenrod Game Corner)
  4. Give target nature parent Everstone
  5. Get egg moves via breeding or Mirror Herb
  6. Give other parent Destiny Knot, breed with 6IV Ditto. Swap the non-Ditto parent with offspring with a higher number of pefect IVs and the correct ability as you go
  7. Hatch with Flame Body/Magma Armor + Oval Charm (4× faster)

Nidoran Breeding Mechanics

Nidoran-F eggs hatch as either sex (50/50).[18]

Nidorina and Nidoqueen can breed (Monster/Field groups). This differs from main games where they can't breed.[4]

Common Breeding Mistakes

  • Breeding with Ditto when you need egg moves (Ditto cannot pass moves)
  • Forgetting Everstone when hunting for specific natures
  • Using Ability Capsules incorrectly and expecting guaranteed Hidden Abilities
  • Ignoring Flame Body/Magma Armor, doubling hatch time unnecessarily
  • Chain breeding when Mirror Herb would be faster

Sources and Implementation Notes

All mechanics in this guide are verified directly against Polished Crystal’s engine logic and scripting. Source links reference the exact routines or data tables used in-game.

[1] Mirror Herb egg move transfer [2] Ability Capsule/Patch and Hidden Ability breeding [3] Mr. PKMN's 6IV Shiny Ditto trade [4] Nidorina/Nidoqueen breeding and egg groups [5] Form and Poké Ball inheritance [6] Egg group compatibility and species parent rules [7] Egg move inheritance rules [8] Hatch cycles and step count [9] Flame Body and Magma Armor hatching modifier [10] Oval Charm and egg production rate [11] Ditto breeding compatibility rules [12] Ditto encounter locations [13] IV inheritance, Destiny Knot, and Power items [14] Everstone nature inheritance [15] Ability inheritance chances [16] Masuda method and shiny odds [17] Shiny Charm interaction with breeding

[18] Nidoran-F eggs hatching as either gender - Nidoran egg gender logic

Author: Cammy and Censoredharp
Last updated: January 30, 2026