Looking for tips regarding how to get the nature you want or a specific egg move? This guide covers everything you need to know about breeding in Polished Crystal!
Author: Cammy and CensoredHarp
Last updated: March 12, 2026
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.
Select a Pokémon above to see its compatible breeding partners
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.
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]
Skewed gender ratios (easier than finding females)
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).
"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
Choose Hidden Ability → Ability Patch/Capsule
Choose IVs → Destiny Knot + 6IV Ditto
Add egg moves → Mirror Herb or chain breeding
Choose nature → Everstone
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)
Get Mr. PKMN's 6IV Shiny Ditto (trade Red Scale from Red Gyarados)
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)
Catch Synchronize Pokémon for each nature you need (Abra at Goldenrod Game Corner)
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
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
Mirror Herb item effect — engine/events/happiness_egg.asm
[2] Ability Capsule/Patch and Hidden Ability breeding
