Biako
To answer the question at least a little. This summoning pen is something introduced along with those golden Tickets in the last update. As far as i understand the functionality is to encourage the writer into writing more, but as far as i know it's no obligation or anything. As i Was not that interested in this that much i didn't Look into it further, so for more information you have to either Look up the notes about the last Update or wait until someone else answers in greater Detail. :)
You meNtioned you dont like writing fillers, Think of it this way. greatest story and film ploT every made was PULP FICTION Anything you write, fluff, filler, side story can be nade into plot armor later in The story. For instance The PuRple lion, the fact that X and Y are aUtonomous beings, even What happens in the book too I hoPe for fortuItous and tumulutous wRiting ✍️👍👍