A "perfect" IV spread in VGC is contextual, not absolute. The naïve definition—31 in every stat—is functionally incorrect for most competitive builds. IV perfection is the alignment of a Pokémon's genetic values with its intended role and the mechanical demands of its matchups. A Trick Room setter with 31 Speed is not perfect—it is broken.

The 0-IV is not a flaw—it is a weapon. A Pokémon with 0 Speed IVs in Trick Room operates at maximum efficiency. A physical attacker with 0 Special Attack minimizes confusion self-damage. The Foul Play interaction—where a lower Attack IV reduces reflected damage—is standard professional preparation. Never breed a Trick Room setter with 31 Speed. This is architectural malpractice.

Egg moves cascade through lineage. A Pokémon can carry up to 4 egg moves, and via Nursery mechanics, these transfer through generations without losing purity. The critical error most breeders make is failing to audit egg move compatibility before beginning the chain. Discovering an incompatibility at step 7 of a 12-step chain is catastrophic and entirely preventable.

The Masuda Method (1/682.7 base, 1/512 with Shiny Charm) is mathematically straightforward but strategically complex. The primary error is not in the calculation—it is in the opportunity cost. The correct approach: breed the perfect IV specimen first, then hunt shinies from that specimen as the breeding parent. Inverting this sequence wastes approximately 87% of session time.

The Destiny Knot transmits 5 of the 12 combined parental IVs (6 from each parent) to offspring. The remaining 1 IV is randomly generated. This creates C(12,5) = 792 possible IV inheritance patterns per egg. A 5IV parent paired with a perfect Ditto yields 5/6 of the IV slots filled deterministically—the target stat becomes the sole variable. Plan for a minimum of 40 eggs.

The Everstone guarantees 100% nature inheritance from the holding parent. Female parent Everstone takes priority. Nature and IV breeding must never be conflated without Everstone—random nature variance across a 5IV hunt is the most common source of wasted eggs in amateur operations. A 4% nature hit rate without locking is not a workflow. It is chaos.

Hidden Abilities (HA) transmit through the female parent at a 60% rate. The male pathway requires an Ability Patch or a male HA specimen bred against a Ditto. A common oversight: breeding a HA female with a non-HA male results in 60% HA offspring, 40% base ability discard. If base ability is non-viable, factor the discard rate into total egg count projections.

Egg groups define the compatibility matrix. Ditto is the universal donor, existing outside the standard matrix—it breeds with any species that produces eggs. Pokémon in the Undiscovered egg group (legendaries, baby forms) cannot breed. Evolved forms share egg groups with pre-evolutions, making pre-evolution breeding the efficiency standard. Smaller sprite, same genetics, faster egg cycles.

EV investment and IV breeding are orthogonal processes that must not be conflated. A freshly bred 5IV specimen begins with 0 EVs. EV training occurs post-breeding via battle, vitamins, feathers, or Pokérus. The professional error is attempting to compensate for IV deficiency with EV investment—the formulas are additive, not substitutable. A 0-IV stat cannot be rescued by EV points.

Speed tier engineering is the most consequential IV decision in competitive breeding. Before finalizing Speed IVs, map the relevant speed tiers: what does this Pokémon need to outspeed, tie with, or undercut? Undercutting—intentionally running slightly slower than a benchmark to outspeed after a single Speed drop—is a legal and strategic IV manipulation. Document your tier targets before breeding begins.