The real question is why at the beginning of the game our ghosts can revive our guardians, presumably dead for hundreds of years, but never attempts to revive the freshly killed guardian on the moon.
English
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Your ghost also does try, and can't at the first cinematic of the temple
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Apparently, he was drained of his light, which I'm assuming makes him no longer revivable.
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My friend was drained of his light a long time ago. Still can be revived by a ghost. His name is Raven(nickname, not gamertag).