The new worldleapers can do targeted dimensional travel, which leaves them strictly worse than the teleport but slightly safer to distribute and, more urgently, is the step before stable dimensional portals. It's a significant breakthrough. He reads the report while flying and he is so excited and he conjures the latest worldleaper prototype and then remembers he's not supposed to leap at random, in case of Materias and so forth, and he still wants to test it so he checks if he has mana for the wizardly dimensional transit spell instead, and jumps.

Check for written works - yep. Not much, so low-tech. Checks for humans - nope, so it can't cheaply be fixed up by going over and dropping vaccines and germ theory - or, at least, it'd have to be a different kind of vaccines and some checking to figure out the relevant germ theory - 

Now he wants to test the new worldleapers, have them target for Warp. He sets up the parameters. 

It drops him somewhere that isn't Warp.

He scowls at his worldleaper, makes a rock in vacuum that he can leap back to, and heads back to the previous dimension, from where he can presumably get to Warp with a standard teleport. 

Except he can't. 

It takes him about half an hour to determine what happened, because he wants to be very very careful with his experimentation. 

Half an hour later he conjures a piece of paper that says letter to Cam: don't make a wizardry teleport with the new experimental worldleaper in hand; I think I leapt two dimensions at once. Can't return to any mapped worlds, I checked. I'm going to leave flags in the worlds I've found. 

Then he throws a tantrum. He's a demon in vacuum very far from any inhabited worlds so it can be a very very elaborate tantrum. He builds entire cities but on fire; he builds other entire cities and then sets them on fire; he feeds all the flaming cities to a sun which he makes on the brink of going supernova; he sits there waiting for it to do that, but gets impatient before it's done and starts messing with its core to destabilize it faster. The sun goes supernova. It hurts. He doesn't heal himself instantly. He teleports clear and curls up and cries.

And then he goes, world to world, leaving flags so if they find any of these worlds they know how to find him, conjuring for the complete works of a Bell.