Zargerth

I don't think Drifblim was meant to do anything besides killing itself. Basically the seed allows it to setup tailwind with no delay then kills itself to allow another pokemon that can use the field/weather/tailwind better to have a safe switch in. This way you can have maximum amout of turns of tailwind with your good pokemon having no downside (no defense drop and item loss) except for the loss of a pokemon( if explosion didn't kill). The premise of a suicide lead. I used an exploding shiftree myself in a sun team myself, very effective.

For the difficulty it is what you expect from Rejuv at this point: legendaries, megas, extremely advantageous fields, weather,... . This creates a situation where if you can use the advanatges yourself it gets ridculously easy like with Amber. Majority of souta's team died to stealth rocks + Silvally flying. I really wish that weather wasn't primal though.

For the story I think the premise was that a hero should abbandon his personal desires for the greater good and that you can't save everybody. The time and space gods refused Melia's request to cure the petrified people because they believe that their sacrfices will in the end be worth (ergo the needs of the few above the needs of the many).  The time and space gods however tried to prove their 'we make sacrifices to protect everyone' mentality by killing almost everybody... . Melia then 'learned' the consequences of her 'naive' behavior and didn't some character growth and we restored the past by correcting her mistake and letting Vivian(?) die.

also my team:

The notion of greater good even with the expense of one/few seems to be present as well. Then there are characters like Melia who are too important to be sacrificed: I had to see how you get Game Over.

I think that explains what that Drifblim is for, then. I led with Meowstic and set up Reflect first so Explosion doesn't KO.

That's... an interesting change, I think. Wasn't expecting his skarmory to get swapped out for a drifblim, but having something easy to drop so you can the big hitters on the field quicker is a fairly sound strategy for a boss. Far less dangerous than Normal's lead on a 1:1 ratio, but more devastating in the long term... Quite the long view Souta's got there, eh?

I do admittedly like his his Normal Mode lead now that I'm not fighting it, though. Its no charge Sky Attacks are absolutely devastating for the unprepared team, especially if it's going first (as it likely will, thanks to the Elemental Seed's Tailwind)- the move packs an increased Critical Hit Ratio, and a 30% Flinch chance to potentially immobilize anything that survives! The fact that it has the Sturdy Ability means that it's largely unfazed by the Seed's Defense drops, and can pop the old God Bird on ya a second time, so chances are that you will lose at least one pokemon to the thing (I ended up slapping an Elemental Seed of my own on my salazzle and using her as a suicide lead, marking the second time I've ever used a Seed myself). Was it the most efficient use of his Tailwind? Certainly not. Was it a darn good first impression? I'd say so!

Anyway, here's my team (since that seems to be a thing here; yes, I've gained a few levels since beating Souta):