@emay
The WN isn't canon anymore. The anime and manga both adapt the LN. The LN and WN diverged so much from each other that you can almost call them different stories. Anyways, this happened in volume 6 in the LN.
@Flavor25 Boy, you’re way out of the fucking loop.
They’re not just some random filler, that’s Apito and Zegion, who will be one of the strongest subordinates of Rimuru, only second to Diablo.
In fact it’s the opposite of filler. Filler is used when you run out of stuff to write about and add-in unimportant bullshit, but in this case, the author left out important information of Apito and Zegion’s origins, because he had too much to write about. You couldn’t be further from the truth.