Imbued Viatality has always confused me to an extent- do cards with HP that don't normally have it lose their HP when Imbued Vitality goes away? If so, are they destroyed because they had HP and it's now dropped to zero?
I believe they lose their HP and are no longer a target. They don't have 0 HP, they just don't have any HP anymore so they aren't auto-destroyed.
While Imbued Vitality is in play though, they have HP and can be destroyed by taking damage that drops them to 0 or below (or by Sucker Punch/Wrathful Gaze or similar).
When Imbued Vitality leaves play it doesn't drop HP to zero, it's just like a character card without a printed value (i.e. the incap sides of Hero cards or Miss Information), they don't have 0 HP they have no HP, they are not a target and are not destroyed because only targets with 0 (or less) HP are subject to destruction due to that.
I think a cleaner way to think about it is that they no longer have an HP value (not that they no longer have HP).
Was there an answer to the originally-quoted question? If something that didn't ordinarily have HP (but did for the moment due to Imbued Vitality) was killed by Haka, could he put that card under Savage Mana?
Any effect that needs a target can affect an 'Imbued Ongoing' and as it's a target at the time it happens yes it can go under Savage Mana.
Haka's diet just got weirder.
I had a game once where we had Imbued Vitality and +1 damage. The Haka player had Savage Mana out. We had an assortment of equipment out and there were some villain targets as well. He played Rampage. Then, he unleashed Savage Mana. I laughed. The villain was essentially finished.
Imbued Vitality can be something of a lifesaver if you don't have any ongoing destruction (or at least, do'nt have any when you really need it). I can remember one time, versus Apostate, jokingly saying something like "Wouldn't it be funny if Imbued Vitality came out and then he played an Apocalypse...", only to have exactly that happen the following round or something. I don't think we'd've been in any particular danger from the Apocalypse (we seldom are), but there was something really quite satisfying about destroying it via punching and stuff :D.