Could the Ghost be Agrus Kos? He has some History as Spirit. And he is kind of an important character storywise, saving Ravnica a few times.
Ghost of Szadeck could fit as well. Probably all legenary creatures that died in Ravnica are a good guess (maybe even Ghost of Kython could be a possibility) if it is Ghost of (legendary creature card name) then it is not Agrus Kos, wojek veteran
If it did have a non-godzila art in magic online then it could be the hinted card as we only have Zilortha as a buy a box card with the godzilla skin
Ghost of Szadeck could fit as well. Probably all legenary creatures that died in Ravnica are a good guess (maybe even Ghost of Kython could be a possibility) if it is Ghost of (legendary creature card name) then it is not Agrus Kos, wojek veteran
Here is a list of all legendary creatures that has no comma in their name (the name would be small enough soo they can simply put ghost of [cardname ]) https://scryfall.com/search?as=grid&order=name&page=2&q=-", " (type:creature type:legendary)&unique=cards