Platinum Spear Pillar
Atop Mt. Coronet, the ruined Spear Pillar is where Cyrus tears open the sky with the Red Chain to drag out Dialga and Palkia. Come back after the story to claim either dragon.
Spear Pillar is in Sinnoh, with Mt. Coronet to the south. In the story it comes after Lake Acuity and continues south to Distortion World.
SPEAR PILLAR MAP
Pokemon Encounters
Dialga
TRAINERS
The summit swarms with Galactic blue. Mars and Jupiter tag-team you in a double battle up to level 46, their Purugly and Skuntank backed by grunts, right before Cyrus makes his move.
Spear Pillar Guide
You can, and that is the big change from Diamond and Pearl, where only your version mascot shows up. In Platinum, after you enter the Hall of Fame, get the Adamant and Lustrous Orbs in Mt. Coronet, and view the Old Book at Celestic Town, a blue rift summons Dialga at Spear Pillar. Beat or catch it, then leave and return for a pink Palkia rift. Both sit at Level 70.
Three things gate the Platinum encounter: clear the Elite Four for the Hall of Fame, collect both the Adamant and Lustrous Orbs from Mt. Coronet, and show them to Cynthia's grandmother by viewing the painting in Celestic Town. The blue rift (Dialga) and pink rift (Palkia) never appear at once, and both respawn if you knock them out by re-beating the Elite Four.