Same dirty strategy.

Grinding your allies is what got you here. Now that your allies are all higher level, you should even get more XP from it.

So you spend the next few days, weeks, months, who knows, continuing your harvesting of monster XP. You would be more lenient to actually siding with them if they didn't still get squashed by almost every hero who walked through. The level difference certainly doesn't seem to matter much to them...

It does to you though. In standard order, each level needs more XP than the last, but you still feel that you're gaining it at a faster rate thanks to the somewhat higher level of your victims. And again you manage to stay unkilled through various strategies and luck.

Eventually you level up again. Not much happens though, as the other dark caster said. You need to be level 7 if you want to be transferred. So you continue. Until the day finally comes...

You're standing around with three goblins, two slimes and another dark caster, guarding a door with some somewhat valuable loot behind. One of the goblins is Gobu, who passes time by blabbering excitedly about his imminent level-up.

"I swear, I can almost feel the XP bubbling in me! It's pretty much ready to convert itself to a tasty, tasty level! Today will be the day, I bet you a month's pay!"

"You don't get paid, dumbass," another goblin replies.

"Not yet, but who knows what the third-tier section holds...! It's closer to the treasure room, so I'm crossing my toes that I'll get a weekly pay of shiny gold coins..."

"What would you spend it on though?" the dark caster asks. "There's no shop in the dungeon."

"Again, you don't know that. And even if not, I just want it because it's shiny. Want to throw it into the air so it can trickle back down on me, coin it over and over, rub it on my-"

He's interrupted by the other two goblins hushing him, as the footsteps of a hero party become audible. They ready their weapons and advance along with the slimes, while you stay behind with the other dark caster. You're about to cast your usual debuffs at them, but you hesitate when you come to think about Gobu being present. He's worked hard for the same goal you have, and he hasn't even been using dishonorable tactics, at least not to your knowledge. Doesn't it feel wrong to take that away from him? Resetting his XP so he has to do it all over again? You would be devastated if someone did that to you...