The choice to use prose with three characters commentating on it was... Not necessarily a bad one, the prose is being witnessed by those characters within the narrative, and otherwise, the prose would basically be a pure infodump. I'm not sure I'd have made the same choice today, but I can definitely see where I was coming from here.
What I do with it being light character based humour and puns based on the also isn't the worst idea, though I'm not really sure my character writing at this point was really good enough to pull off the effect.
All in all, this isn't as bad as I was expecting it to be rereading it, but it's broadly speaking just an infodump in which nothing actually happens aside explanation of the rules for the next chapter.
I also don't hate the idea of the poem at the end, but the syllable count feels off for the final two lines (and it should be too rather than to). No clue why they all end in semi-colons either. If I were to do a very quick rewrite:
Five lines in all
In ev'ry ten,
Of both pain and joy that bring.
But stay too long
And power lost,
You become a toy again.
But even then there are elements I'd want to revise - It's a very... Prosey... poem, for want of a better word. It doesn't really play with the sound of language.
I also don't hate that there's no attempt to explain how it exists in universe aside from being 'a warning from the multiverse itself'
Honestly, it's a shame my plans for this segment of Sandy of old got upended by exams. While the opening is... At best fine and at worst meh, I do like the idea of a cold war between a Pikachu with Narrator powers and three more powerful entities who used to be mortal characters but can only interact with the world for five lines at a time, and playing with line counts as a limitation on a character's ability to act is fundamentally the same core concept as Joey only being able to remain out of his PokéBall for 10 lines at a time before the Sand Reaper appeared.