unfortunately, i haven't played many of the events that focus on Grimnir and related characters so i am not sure the details on his relation to Odin and such atm.
In regards to Bahamut, he basically just wakes up and decides to destroy everything lol. there isn't really anything deep to it. In the 10th anniversary event, the "true" Bahamut wakes up (all the other Bahamuts that showed up in previous events were just fragments of the real one), destroys Mystalsia and almost everyone who lives there -> Mystalsia is broken into fragments (which are parallel Mystalsias, basically what-if worlds) and, in order to save the true Mystalsia, those fragments need to be united into one + need to defeat the true Bahamut so that he doesn't completely destroy Mystalsia.
As for recommended events, the anniversary events are good to play so i will list them here for convenience and put some notes about them
導きの妖精姫と世界救う剣 (The Guiding Fairy Princess and the World-Saving Sword)
去りゆく君への鎮魂歌 (Requiem for You, Who Has Departed)
終焉に抗いし時越えの精霊 (The Time-Crossing Spirit Who Defies the End)
汝、永遠の終わりを告げる者 (You, Who Marks the End of Eternity)
These are sequel to the 2nd anniversary events. I posted translation of them here.
巡る時の物語 (Story of Cycling Time)
いつか、重なり合う未来へ (Someday, Towards the Overlapping Future)
This one deals with some problems after what happened in 3rd anni but also features various other characters and references other events due to the nature of the story.
君と僕の終わりの物語 (The Story of the End of You and I)
This one continues story stuff from Gleaming Knights series of events and New World series of events so i'll list those here
the Gleaming Knights events:
But tbh, the only events of the Gleaming Knights stuff that are actually relevant to the 5th anni story are 天威の双手 and 未来を紡ぐ者. These two you definitely need to play before the 5th anni event.
the 5th anni event is direct continuation of this line of events!
終焉、天より来たりて (The End Comes from the Heavens)
黒銀、影より羽撃きて (Black and Silver Wings Flap from the Shadows)
i haven't finished playing this one but it'd be good to play the prev events centered around Supine beforehand.
交わる世界、巡り合う刻 (Intersecting Worlds, Chance Meetings)
審判の槍、再来の剣 (Judgement Spears, Returning Sword)
あなたに捧げる最後の願い (My Final Wish to You)
The characters are in modern day Japan for some reason! You'd want to play the 2nd and 3rd anniversary events for Lucifer's story and the 5th anniversary event beforehand. It also would be helpful to know the basis of certain other characters that appear (Lucius, Teena, Amelia, Cerberus).
Mystalsia Festa！～ミスタルシアフェスタ～
舞い降りる却炎と集う光闇 (Falling Flames and Gathering Light and Darkness)
i haven't played these yet but like literally every shinbaha character appears... the first part is very laidback while the second is more serious plot (since a certain dragon shows up...)
This event is completely disconnected from any event before it so it can be played at any time! also this is my fav event so i recommend it heavily
終焉の創生竜と重なる希望 (The Genesis Dragon of the End and Intertwining Hopes)
Should play at least 9th anni event before this one.
In regards to the events listed on the character pages, they used to be in proper order but now it's super messed up bc they replace the original events with the rerun versions on character pages so they end up in the completely wrong order bc it uses the date for the rerun rather than the original... it's better to look at the "related events" on the event you want to play. the events there are ordered from bottom-top = oldest-newest. tho they will list the original event and the rerun event as separate so it will list the same event(s) twice if they have a rerun version. though, you can't reference this for the anniversary events specifically bc they don't show the proper connected events for them.
other than that, an easy way to figure out proper order is to look up the names of the events you want to play and check when they originally came out and then play them in release order. the official 10th anniversary website has a timeline that lists all events in the order they released up until August 2021 so it's pretty helpful for that purpose. hara-pan also has pages collecting all events from each year.
And yes, feel free to reach out any time!
origamiaround
turnnoffyourmind
janainaart
snowghoul
yousharknotpass
annaxmalina
jacobvanloon
