u/Unlikely_Cloud4013

hi y'all~! for anyone who's played this one, could you help me work out this puzzle? I figured it had something to do with Grimer, who learns Moongeist Beam, Moonlight, etc. by level up, but yk... it didn't work. I've practically almost complete the dex and I can't find anything on this one, everyone seems to just skip it.

Complete the entire game up until after Fuchsia Gym (after which you can't progress until in a couple of days when the rest of the game is scheduled to be finished) so just confused as to why i'm stuck here lol thanks y'all