Question

I'm reviving the ancient game of Pokemon XD: Gale of Darkness. And I am wondering how to purify Lugia, if possible, so I transfer and such.

Answer 1

You can only purify Shadow Lugia by putting it in the Purify Chamber. The purification will be instant. However, all 9 Sets of the machine must be running on max efficiency.
Source: http://bulbapedia.bulbagarden.net/wiki/Shadow_Lugia#History and experience.

Answer 2

You purify Lugia the same way you purify any other shadow Pokemon.

Source: the bulbapedia article about shadow Pokemon (it had stuff about lugia but didn't say anything special had to be done to purify it)

Comments

That takes too long, is there a faster way?

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I don't think so but, I'm not an expert on that game

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You should give this answer BA. Even though it may take awhile, it doesn't mean that this isn't a good answer.