I'm leaving some idioms that require the gravity rune untouched, only because they can still fall in to mid-tier. One is just a laser beam, which is one of Myron's only offensive spells, the second being a deathtrap rune that is difficult to create regardless. Gravity rune is practically just a vaccuum, the same effects could be produced by wind pressure, but I'll leave it out to save mind.

Now comes the real issue... making a neutral good character have a reason to kill another random neutral character. Luckily I have a good imagination, and Myron's canon story can send him off with a touch of information that might have been metagaming under any other circumstance. Hope that doesn't have you worried, he won't know anything about Corban upon their meeting.