Spear Pillar

Spear Pillar made it's debut in Pokémon Diamond and Pearl where Dialga and Palkia can be captured. Arceus can also be captured at Spear Pillar in the Hall of Origin in Diamond and Pearl.

Spear Pillar has been confirmed to appear as a playable stage in Super Smash Bros. Brawl, apparently Dialga, Palkia, and Cresselia appear in the background to devastate the players, screenshots can be seen here. It is a destructible stage, and features a cave underneath the surface which players can enter.

Also the Lake trio Pokémon appear Mespirit, Azelf and Uxie when something happens to the stage.

How to Unlock
Complete Event 25.

Stage Elements
After the first few seconds in battle, Dialga (Common), Palkia (Uncommon), Cresselia (Rare) or Arceus (Ultra Rare) shows up in the background of the stage. The Pokemon do different actions such as:

Dialga: Horizontal beam on the lower section, vertical beam covering 1/3 of the stage, Roar of Time (jumps into the stage and damages anyone near Dialga), break the middle part of the top level

Palkia: Same as Dialga, except uses Spacial Rend instead of Roar of Time.

Cresselia: Shoots a boomerang-like energy blade, which randomly goes around the stage, or uses Psycho Cut(shoots waves straight at the top platform).

Arceus: Uses Judgement, OHKOing anyone on the top platform.

Links

 * Video Footage and Music Confirmation.
 * Proof of Cresselia.
 * How to Unlock!