*He glances at it, frowns, flies over to examine it, then flies back.*

Some kind of teleportation magic gone wrong?

*He can tell what it's supposed to do easily enough. There's so many different kinds of portal magic in use in his underworld (not to mention how much they could have changed in the two thousand years he was gone) that he doesn't even bat an eye at not recognizing the specific spells...but it doesn't look like any kind of standard setup for a summoning ritual to him.*