Huh saw these spoilers on reddit like 2 days ago, didn't think they were legit. Guess they are.
So the horn. If someone toots this horn, are we going to get another massive haki blast that will completely overwhelm Imu's maki? I hope that isn't going to be reused so rather, here are some alternative suggestions:
A. You toot the horn near a poneglyph, it translates it
B. It actually is a weapon. It plays frequencies that Imu and his minions are weak against. Think apoo but just specific to wielders of maki. (No, I have not played Destiny).
C. It doesn't do anything useful but it does play a loud victory tune. It turns out to be a relic tech from the AK that sound dials are based off of.
Yeah can't really think of anything else but A seems possible yet unlikely because that job is saved for Robin already and will really take away from her development and to another extent, ruin the use for the 3rd eye for pudding. I personally like C the most because B is just another "savior" that arrived to save Luffy again as Gaban and Hajrudin did.
However this really all leads to one main question: who is supposed to use this horn? Google and spoilers point to a very specific norse god that uses this horn to sound the arrival of Ragnarok. Will the horn be used to signal to everyone that the big war vs the WG has finally started AFTER the big decisive events of Elbaph? Again, just who will use it? Loki is the god of mischief, it aint him so... yeah I been saying who who who so many times I might as well throw in a wild guess and say Biblo but could bro even blow a horn? Biblo is a pretty legendary creature here in Elbaph afterall and he guarding the books which is a "bridge" between "worlds". What I mean by that is literature is a way for the past to speak to the present and with such knowledge that the WG is trying so very hard to burn...more than once! mind you, anyone can surmise that these precious books is a literal bridge from past to present so it makes sense for Biblo to play the flute in my opinion.
Edit: Well shit. I guess my very sentence of this post was accurate after all damnit.