I don't normally scream about other people's rottmnt au on here, but @somerandomdudelmao 's Cass Apocalypse Au is driving me up the wall, and I have words!!
Everyone who is reading the series knows it is currently in the process of Casey Jr. resurrecting his uncle/dad's.
Theory Time!
First off, let's go into why Casey can do this.
Yes, Cass has confirmed that the memory spell that was used was mixed with a time travel one. Thus, using one's memory's as a gateway to not only traverse time but dimensions.
However, Casey Jr. is able to see spirits when he does this but also remains physically in the present - which leads me to think that he is being astroprojected across time and space as a literal spirit. Hence why he can visit his memories and the past without altering the events on a physical level. As a spirit, Casey Jr. can see and engage with other spirits in existence at that time.
In the powers of spirit to spirit interaction, he is the only person alive who can literally pull other spirits through dimensions. With his body anchored in one time branch and his memories anchored in the other one, Casey Jr. Is the literal bridge for spirits to cross from one to the other.
No matter the condition of the spirit.
Theory #2
Cass has shown us F.Mikey communing with his ancestors when Donnie originally pasted on. It also was largely suspected the krangg could destroy ninpo and spirits.
With the Hamatos, spirits and ninpo are consister linked if not one. So, of course, when Casey Jr. travels back to his past in his time branch and is able to intact and unintentionally pull Donnie's disintegrating spirit into and out of time with him; Casey Jr. effectively saved Donnie's ninpo. Immediately after his recuse, Donnie admits that his NINPO is in shambles and that he is doing everything in his power to hold it together.
With this confirmation in mind, let's have a look at the conditions surrounding the other turtles' ninpos and spirits.
First off, Raph
Raph's spirit and ninpo were perfectly healed and intact with in the robot body Donnie created for him. The only thing is that Raph's 'body' could be turned activated or shut down. Like a Fullmetal Alchemist parallel, Raph's soul, spirit, and ninpo are housed within a metal container. In episode two or three, when Casey Jr. found the robot, Raph was reactivated after an emergency shutdown that lasted YEARS.
His ninpo and spirit woke up. Know that, shutting himself down again to allow his generator to be redirected as a power source would not kill Raph but rather put him to sleep. He would never die but remain suspended for all time, trapped in his metal shell until someone reactivated him.
This made Raph not only be the easiest but most accessible spirit for Casey Jr. to rescue. Raphs' spirit would have remained there, in perfect condition, for however long it took for Casey to get to him.
Now, let's look at Mikey.
This old mystic warrior was the most in tune and most powerfully adept with his abilities. Drained he may have been, Mikey said that opening a time gateway would use whatever he had left. His mystic powers and ninpo are linked. Opening the time gateway was a strain on his spirit, his ninpo. He was literally splintering apart as he opened the portal. In Mikey’s moment of death, he pushed the last of his ninpo in the portal. His ninpo burst like a firework.
At this point of this written theory, Mikey's has not been rescued.
This leads me to speculate the condition and difficulty of said rescue for one Casey Jr. Mikey's soul is untrained by Krangg's chemical warfare, so it is not in danger of disintegrating but nor is his soul bound to a metal shell, his spirit is actually free to reform and rejoin his Hamato clan.
This leaves Casey Jr. vary little time to connect with Mikey's spirit. There is the option that he will witness Mikey's ninpo shattering into a million pieces. However, he may also be witness to Mikey's ninpo, in stark contrast to Donnie rapidly decaying ninpo spirit, pull back together. In glorious younger self. All golden and whole.
All that training and usage of his ninpo would have given his spirit and ninpo the ability to reform faster than one that was infected with a ninpo-distorying illness. This moment, where Mikey spirit lingers before ascending or choosing to join with his ancestors, Casey would have to approach.
Then again... Mikey could also rather stick around and wait for Leo to join him.
Option 2 is that when Mikey explodes, Casey Jr. would have to act fast to catch the ninpo pieces upon explosion. I like option number one a lot better.
Regardless, Mikey could be a time sensitive rescue. Mikey is quite literally a wild card in this realm.
This brings us to Leo.
Can you see where I'm going with this?
It's not a secret that Casey has related to Younger Leo about how his future self was a shield for Mikey's ninpo.
F.Leo is shown to have sacrificed the use of his ninpo, or lack there of, to draw the Kranggs apparently one-time-use ability to lock or damage ninpo/magic on to himself to free Mikey to mystically blast Kranggs to oblivion. In contrast to Mikey's fully intact Hamato ninpo, Leo's utterly demolished ninpo is in full view for us to see .
How it got way we can only speculate - but it may have been sacrificed to help Mikey originally and never fully recovered. F.Leo even claimed once, after using his ninja skills of speed to confuse and irritate Krangg into using that ninpo destroying sonic wave they have, that he had no magic or anything for them to destroy.
So here is the thing. If a Hamato spirit and ninpo are one in the same... where does this leave Leo's spirit? His soul? His ninpo? It's all in pieces, broken, destroyed. Claimed to no longer exist. But the pieces remain.
They are pieces in a container. Like how Raph's spirit and ninpo were contained in metal, Leo's broken ones were still collected together within his living body.
So what happens when Leo's body is incinerated by that krangg's beam death? Like his twin, Leo’s spirit has been affected by the krangg and was unable to heal. There is no holding himself together here. He is most likely already like clear glass like pieces on the breeze or scattering in the wake of the after math. Destined to fade from existence.
He's the most likely to join his Hamato ancestors immediately, but without the ability to pull his ninpo together on his own, Leo would take time to reform with the Hamoto Clans help.
If Casey is to save Leo's ninpo and spirit at all, he would have to find away to collect the pieces of Leo's shattered ninpo once the beam hits.
Another problem, if Kraggs technology has the effect of destroying one's spirit, Casey's astroprojected spirit could be in danger if that death beam gets too close. He wouldn't be able to save his sensai and himself if that is in the way and active.
Saving Leonardo's shattered spirit and ninpo would not only be near impossible, but a definite risk to Casey Jr.'s own spirit. Astroprojecting his spirit still puts put's his life in clear physical danger of coming in contact with spirit damaging tech. Saving any remnant of his sensai's spirit and ninpo is going to acquire a plan. Or dumb luck.
That being said... Donnie is our evidence that even in pieces, Leo could be saved. Casey Jr. would have to get dangerously close to the death beam. That or stand among the lingering pieces of Leo's soul as they float for a moment in the aftermath. In any instance, all Casey Jr. would need to do is come in contact with any of these spirit partials, and they would all be sucked up in to him.
Unfortunately, I'm not sure Leo's broken spirit would be overly responsive to any of Casey' Jr. 's concerned shouts, if at all. But Casey would be able to feel him.
On returning to the present, we know from Donnie that krangg effects are left behind. This would result in two ways of Leo being resurrected.
1. On returning to the present, Casey would scramble for the cloning tube and instantly deposit the ninpo fragments. Leo would return with a new body shell for his broken bits. In this case, Leo would probably be comatose for a good long while until his pieces, now cleansed from anything krangg, reform and heal in safty.
2. Leo's ninpo is too weak to transfer into his clone and takes refuge in Casey instead until his cleansed ninpo pieces find a way to pull together. Maybe with help from Mikey?
Also, could Casey house two Hamato souls at once? Since Mikey and Leo practically died at the same time.
Because to wrap horribly long theory thread, I would almost expect a spirit Mikey to tell Casey's to grab Leo first then come back for him as Mikey's spirit is safe in the aftermather of the death beam. If Casey housed two Hamato spirits at once (headache just thinking about it), then Mikey mystic warrior aspect could collect and even help mend Leo's shattered ninpo.
But in conclusion, F. Leo is the most at risk and dangerous Hamato spirit to rescue. Logic states that there would be a possibility that F.Leo may never get rescued and be a lonely turtle spirit with his ancestors after. However, this is Cass's Au and Donnie of all people is defying logic. So I predict that some kind of Dumb Luck option from above will be Leo's saving grace. I just feel Casey Jr. is going to have a few singe marks on his soul to tell about when all this is said and done.
TL:DR - Raph was the easiest turtle to rescue as his spirit was stuck in a tin can. Mikey is a wild card in terms of spirit condition, but saveable on a time limit. Leo is the most riskiest and dangerous to save with a broken ninpo.
Casey Jr. and Donnie have no fear.
Live on future turtles!
