Salamud

He's both unneeded to Fates' overall plot and together with Garon does too much in it.

The Twelve Visitors and Loptyr aren't called dragons until GotHW's end, the news being treated as a surprise. Since Duma's appearence in both Gaiden and Echoes is a rotten dragon, I would call him and Mila dragons.

TRS was started as another game in Marth's world happening around the time of Dark Dragon. It still has the detail of its continent being settled by migrants from a suspciously named Jugd. All considered it's acceptable as a source for any plans Kaga might have had for lore.

Kaga's later work (Tear Ring Saga) had dragons worshipped as gods. So, I wouldn't rule out Duma and Mila being dragons.

You could just cut out the time traveling Children and have Tiki get messages from the Future.

Yes. Medeus is an Earth Dragon. He transforms into a monster associated with the darkness of the underworld. Duma is a Divine Dragon. He transforms into a monster associated with the putrid dead.

I figure it's just the Divine Dragon version of a Shadow Dragon. Echoes points to Divine Dragons having an affinity towards life (enriching soil, triggering swarms of zombies). Being a dark form of Divine Dragon makes Duma's current status looking so decayed fit.

Here's a post I made in another topic discussing the overall plot. I'm sticking with what I posted. I'm curious about any extra views:

Alm doesn't act like Walhart even when Celica isn't around.

Putting onto Thane's post, I'll say that Jedah was wasted potential. When he first approaches Celica, he actually has a bit of a point. He say the dragon gods are degenerating (which is a plot point that ties in nicely with the rest of the series' depiction of them), and so we need you to sacrifice yourself to fix that Now, the overall story pushes for "Death to the gods! We don't need them anymore!", and that's also a point. But Jedah's proposition, on its face, isn't a terrible offer either. Celica even calls it "too good to be true". Unfortunately the scene goes downhill quick. Jedah talks about creating a nightmare world under the restored Duma by sacrificing Celica to Duma, in front of Celica. First off, I'm not seeing what makes Jedah figure a restored Duma would help with his chaos filled nightmare world plan. Not only do we see that Rigel for all its flaws isn't like that but Duma himself obeyed the pact he made with Mila and overall tried to avoid going to war with his sister. Frankly, the corrupted Duma would be better for spreading chaos. Secondly, what makes Celica figure that Jedah would keep Alm safe and not screw over Zofia even after hearing his plan talk? You could have just made Jedah try to make Duma Great Again so that he'll keep Rigel strong and also get revenge on Zofia for not helping them during a famine (maybe even put a parallel with Chrom not letting Robin kill himself to stop Grima for good). You could have had him trying to turn the continent into one fit for Duma. You could have even had Jedah not do his dastardly plan talk when Celica was looking. But nooo.

Gaiden being selected as the 3DS remake might have something to do with being so easy to translate into the engine used by Awakening and Fates. So, what game gets selected as the next remake might depend on what Switch FE turns out to be. Putting it another way, we should wait to find out if Switch includes Children, Total Wide Maps, or even Dungeon Crawling.

Mila being sealed away triggered the undead walking. Considering that and Mila's overall portrayal, I'd just say Divine Dragons have an affinity towards life which can be corrupted into an undead army. As demonstrated by Duma (Corrupted Divine Dragon), Grima (construct made with Divine Dragon Blood), and their followers.

An issue here is that Fire Emblem is a game focused on war. Short of Warp, beating maps without slaying enemies isn't really doable. Battle fixes whatever problem is happening in FE more often than not. Alm might be gung-ho about facing Rigel, but Rudolf and Duma masterminded the war with Berkut egging on Desaix's coup. And he still pursued diplomacy with Rudolf turning him down. Alm is never at a point where he questions his life of war. He himself never faces a downpoint of living by the sword. Celica by contrast is the one who gets humbled.

Loptyr never demonstrated he or his minions had any control over undead beyond the Deadlords.

I don't see the issue. Duma is more associated with decay and the undead. Medeus and Loptyr are more about darkness.