Over on his workblog, Journey Into Mystery writer Kieron Gillen explains his use of magic in comics:
When you come to pure unprecedented magic… it’s something I try and put on the table as early as possible, at least subconsciously. For minor stuff along the way, you can get away with it (For example, Hela re-arranging her fortress), but for big stuff the plot turns on, you want to introduce it as early as possible as a possibility. To choose an example from THE FINE PRINT, in the final issue Thor gets his mother Gaea to reject the sword from the ground. Now, I could have written that scene and just had Thor done it. As in, Gaea’s his mum. Why not?
Well, Gaea being his mum wasn’t an element in this story. The only people who would have gone along with it were people who’ve been reading Thor forever – and probably not even them. So, in the previous issue, I have a scene where Gaea appears to being tortured in hell. At the time, this appears to be a moral challenge for Thor – as in, can he leave his mum here? And it absolutely is – but for the story as a whole, it’s about introducing the idea of Gaea being part of even Hell’s soil, so Thor’s solution at the end isn’t a deus ex machina.
For me, if a story’s conclusion involves a magical ability which hasn’t been put into play in advance, it’s probably a story that doesn’t work. Probably.
I like that Gillen’s magic rule is essentially just good writing: “Don’t pull something important out of thin air at the last moment.” (I’m not being sarcastic; I wish that more writers would bear that in mind when writing magical characters.)
There’s more at the link, including why Journey Into Mystery doesn’t necessarily fall under the same rules, and a promise for a more in-depth post at some point about “something a little bit craft-y involving comics, specifically about compression and decompression,” that I can’t wait for. Go and read.