After you get the Arceus event where go to him on Pokemon diamond?

You can't get Arceus in Pokémon Diamond or Pearl through a regular event. Arceus is only available through special events that have long since passed. You can only get Arceus on Diamond and Pearl by trading it from another game where you obtained it through an event.

Here's a breakdown:

* No Regular Arceus Events: Arceus was never a regular encounter in Diamond or Pearl.

* Past Events: Arceus was distributed through specific events in the past, usually tied to specific dates or promotional activities. These events are no longer active.

* Trading: The only way to get Arceus in Diamond and Pearl now is by trading with someone who obtained it through an event in the past.

If you're hoping to get Arceus in Diamond or Pearl, your best bet is to find someone willing to trade you one. You can try online communities or forums dedicated to Pokémon trading.

Note: Arceus can be obtained through events in later Pokémon games, such as Pokémon Black and White 2, Pokémon X and Y, and Pokémon Omega Ruby and Alpha Sapphire. These events might be re-released occasionally, so keep an eye out for official announcements.