This is somewhat reminiscent of Schismotivate, but no, I don't think I've seen a blue spell do both -X/-0 and +0/+X on the same card, even though blue does have access to both halves of that. (Well, OK, there's Defensive Stance and all the Morphlingalikes. I mean give the two halves to two different creatures.)
For Challenge # 070. A poor man's overrun :)
This probably doesn't need to be rare, nor in dragon's maze, but I was surprised to realise that (AFAIK) overload spells can do that but haven't yet.
Is there an existing non-overload version?
This is somewhat reminiscent of Schismotivate, but no, I don't think I've seen a blue spell do both -X/-0 and +0/+X on the same card, even though blue does have access to both halves of that. (Well, OK, there's Defensive Stance and all the Morphlingalikes. I mean give the two halves to two different creatures.)
Oh, good call on double overload. In retrospect, that seems like something that should have been done in RtR...