Just playing a
rush in Gold and I had an invulnerable Seraph in the middle, and a Minor Phoenix on either side. The AI played Dessication which didn't affect the Seraph but killed both Minor Phoenixes and turned them into Ash. I Cremated one Ash and played a Seraph in its place. The next turn I resurrect my pile of Ash and I get an Unupped Phoenix. The extra 3 damage didn't make any difference, as it went, but I'm sure that an Upped card is supposed to remain Upped.