Shadow Rhyperior IV Compromise — How Far Can You Go in Master League?

Why attack 15 matters — CMP

Master League has no CP cap, so everyone is max level. When same-species (mirror) or same-stat Pokémon fire a charged move on the same turn, the higher effective attack goes first (CMP). An attack-14 Shadow Rhyperior loses that priority to an attack-15 opponent. In the sim, the attack-14 mirror came out 0-shield=loss, 1-shield=loss, 2-shield=tie. In a mirror-heavy meta, attack 15 is effectively mandatory.

Where win/loss starts to split

Shadow Rhyperior is IV-tight. Even dropping to 15/15/14 starts losing Xerneas. Across the full top-100 sim, small stat cuts cross breakpoints and flip matchups, so a high-IV catch is the safer play here.

Best Buddy — depends on whether the opponent is too

Best Buddy (level +1) depends on whether the opponent is best-buddied. Against a non-best-buddied opponent (L50) you newly win 4 matchups at 1 shield; against a best-buddied one (L51), 0. Top Master legendaries are usually best-buddied, so the mirror and same-stat rivals go back to a tie when both are L51. It never hurts, but it doesn't magically win the mirror.

Note that this line moves with the meta. If usage shifts or a new Pokémon arrives, the breakpoints move and a spread that's fine today can get shaky. This analysis is for Season 27 (2026.06.02~09.09); when the season changes we re-run the full top-100 sim and update it.