Generation 1 · Pokédex profile
Rock Snake Pokémon
Pokédex entry
There is a magnet in its brain that prevents an Onix from losing direction while tunneling. As it grows older, its body becomes steadily rounder and smoother.
Battle data
Conditional evolutions can require additional game-specific prerequisites beyond the displayed method.
| Method | Location | Level | Evidence |
|---|---|---|---|
| Grass / ground | Cliff Edge Cave | Lv. 23–26 | Source-indexed, not individually verified |
| Grass / ground | Johto Victory Road 1f | Lv. 38–40 | Source-indexed, not individually verified |
| Grass / ground | Johto Victory Road B1f | Lv. 40–41 | Source-indexed, not individually verified |
| Grass / ground | Johto Victory Road B2f | Lv. 41–42 | Source-indexed, not individually verified |
| Grass / ground | Mt Silver 1f Item Room | Lv. 62 | Source-indexed, not individually verified |
| Grass / ground | Mt Silver 1f Moltres Room | Lv. 62 | Source-indexed, not individually verified |
| Grass / ground | Mt Silver 1f Waterfall Room | Lv. 62 | Source-indexed, not individually verified |
| Grass / ground | Mt Silver 3f | Lv. 62 | Source-indexed, not individually verified |
| Grass / ground | Mt Silver Mountain Side | Lv. 68 | Source-indexed, not individually verified |
| Grass / ground | Rock Tunnel 1f | Lv. 13–15 | Source-indexed, not individually verified |
| Grass / ground | Rock Tunnel B1f | Lv. 13–17 | Source-indexed, not individually verified |
| Grass / ground | Safari Zone Low Mid | Lv. 19–26 | Source-indexed, not individually verified |
| Grass / ground | Seven Island Sevault Canyon | Lv. 54 | Source-indexed, not individually verified |
| Grass / ground | Union Cave 1f | Lv. 8–9 | Source-indexed, not individually verified |
| Grass / ground | Union Cave B1f | Lv. 8 | Source-indexed, not individually verified |
| Grass / ground | Union Cave B2f | Lv. 22 | Source-indexed, not individually verified |
| Grass / ground | Victory Road 1f | Lv. 40–46 | Source-indexed, not individually verified |
| Grass / ground | Victory Road 2f | Lv. 45–48 | Source-indexed, not individually verified |
| Grass / ground | Victory Road 3f | Lv. 40–46 | Source-indexed, not individually verified |
Rare grass and Surfing encounters inherit the first native slot's level range. Supplemental fishing follows each rod's native slots. These ranges exclude Lure effects and randomizer replacements; eligibility restrictions still apply.
Data source: configured Grand Anthology Gen 1–9 species, forms and abilities. The website uses frame-cropped copies of the game's existing Pokémon sprites, which remain franchise/artist-owned assets. Some alternate forms use labeled default-form artwork when their individual sprite is unavailable. See acknowledgments for credits.