World Axle - Deepest Level (Japanese: せかいのはしら さいしんぶWorld Pillar Deepest Part) is the twentieth and final region of Pokémon Rumble Blast's story. It consists of nothing but a five-stage Team Battle, in which Cobalion will assist the player in defeating Dark Rust. All Pokémon found in this region are rusted.
No Ⓟ is given during the first completion of Dark Rust's Fort.
When Cobalion and the player's Toy Pokémon enter Dark Rust's Fort, several Hydreigon and a Dialga controlled by Dark Rust can be seen in the background. However, none of them can be seen in the actual Team Battle.
The glowdrop dropped by Zekrom in Dark Rust's Fort restores more HP than usual.