Can I rebattle Dialga in the original Pokemon Diamond game if I killed it?

Question

I wanna shiny hunt Dialga in Pokemond diamond (not bdsp) but I don't want to do it now, can I rebattle Dialga after I beat the Elite 4 or is it gone forever if I kill it at my first encounter? Thank you for help :)

Answer 1

Yes, if you go and talk to Dawn after beating the elite four she will say that Prof. Rowan said that it may have appeared on Mt. Coronet again, thats what happened to me.

In Diamond and Pearl, this new rule applied to Dialga and Palkia only. In those games, entering the Hall of Fame causes them to respawn.

You will have to talk to Dawn after you defeat the Elite Four, then it will appear on Mt. Coronet again.

Source

Comments

Bulbapedia says that they can reappear in Platinum but not any of the older games.

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Where does it say that?

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> Changes from Diamond and Pearl
If the player defeats a stationary in-game event Pokémon (including most Legendary or Mythical Pokémon), it reappears next time the player enters the Hall of Fame.
https://bulbapedia.bulbagarden.net/wiki/Pok%C3%A9mon_Platinum_Version

> Starting in Pokémon Platinum, if the player defeats or runs from an in-game event Pokémon, then it reappears next time the player enters the Hall of Fame.
https://bulbapedia.bulbagarden.net/wiki/List_of_wild_Pok%C3%A9mon_from_in-game_events

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This does indeed work on the original pokemon diamond. Not just platinum.
I have confirmed this with both a ROM copy of Diamond by killing dialga and it reappearing at Mt Coronet and
with an original Diamond cartridge by blacking out against dialga and it still being there upon returning to Mt Coronet.
There seems to be a lot of misinformation about this and as I was attempting to RNG manip a shiny Dialga but forgot to set up for it prior to getting stuck on Spear Pillar, I did a bunch of testing of this myself.
This has been corrected on bulbapedia:
>In Diamond and Pearl, this new rule applied to Dialga and Palkia only. In those games, entering the Hall of Fame causes them to respawn.

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thank you for your testing and research Yixlid! I edited the answer to include the quote you posted. Would you mind posting the link to the bulbapedia article you got that from so I can also site it properly?