Holy crap, I haven't really been paying attention to the amount of reads this story has been getting. Thank you all for the 70k reads.
Most of the fighters in the area was shocked at (Y/N)'s idea.
Harribel: A shinigami using resurreccion? Is that possible?
(Y/N): It is. Sung-Sun could back me up on that one.
Sung-Sun: Indeed, Tosen used a resurreccion against us.
(F/N): It should be possible. (M/N) was an arrancar that used a Bankai, so the opposite should be possible.
Starrk: Then let's get started. We don't have much time.
Harribel and Starrk then started to explain the process of resurreccion to (Y/N).
Starrk: I guess to explain what resurreccion is... you have to release your full power...
Lilynette: You need to explain it better than that you idiot!
Harribel: I guess a better way to explain it is that resurreccion is an arrancar's way of unleashing the true ability that we've sealed off prior.
(Y/N): But I've been at full power since I've been in Bankai...
Apacci: Yeah you're at your full strength as a Shinigami, but what about as an Hollow?
...
...
...
Apacci: What? Why is everyone so silent?
Sung-Sun: Sorry, but we just weren't used to you saying something intelligent for once.
Mila Rose: I agree, this is a pleasant surprise.
Apacci: I'll knock you both out!
(Y/N): You make a good point Apacci. I didn't think of it like that.
(Y/N) got into a meditation pose.
(Y/N): If anyone knows how I can draw out my Hollow powers, it's my own Hollow. I'll see you guys in a bit.
(Y/N) started to meditate. Starrk turned towards Unohana and (F/N).
Starrk: I suggest you move the injured far away from here.
Unohana: Is there a problem were they are now?
Starrk: If (Y/N) is planning to learn resurreccion then his first time transforming may make him similar to any other hollow. Wild. Acting on instincts.
(F/N): If what you said is true, then (Y/N) may very well transform into a Vasto Lorde...
!!! Harribel: What makes you say that?
(F/N): (M/N) was a Vasto Lorde too. There's a chance it may be genetic.
Unohana: A Vasto Lorde on the loose isn't good. Mr. (L/N), may you help me move the injured to a safer location.
(F/N): Just (F/N) is fine. And sure.
(F/N) picked up Urahara and Yoruichi's body and moved them in a safe location while Unohana went back for the other Court Guard Shinigamis.
Harribel and Starrk stood directly infront of (Y/N) while Mila Rose, Apacci and Sung-Sun stood behind him.
Harribel: What do you think our chances of success are?
Starrk: In surviving against (Y/N)? Not sure. He may very well become a Vasto lorde with a Bankai which means he'd be stronger than a normal hollow.
Harribel: I see.
Starrk: Are you having second thoughts?
Harribel: No. I trust (Y/N) to succeed.
Starrk: I see...
All the arrancars were on alert, waiting for any sort of change in (Y/N).
In (Y/N)'s inner world.
As (Y/N) entered his inner world, he felt himself falling.
Although his inner world was shown to be in the clouds, this was the first time (Y/N) ever fell out of the sky in his inner world. (Y/N) immediately flew towards the floating palace, that was also falling out of the sky. He wasn't completely sure but if what Ankou told him last time he was here was anything to go by, then this must be the result of the stress and pressure he felt fighting in the war with Aizen.
As (Y/N) touched down on the falling palace, he met face to face with an enormous Hollow.
"You're finally here."
"You can talk?"
"Don't tell me you don't recognize me, Overseer."
Hearing the nickname, (Y/N) immediately knew who he was.
"You're (Y/N)..."
"Correct but also wrong. I may be your hollow powers but every spirit has their own identity. Let me officially introduce myself. I am Thanatos, your hollow powers. If I were to be more specific, Thanatos is the name of your resurreccion."
"I see. Considering you're here, you know what I came to do?"
"Of course. Although, before we start, we need to talk about the elephant in the room."
"You mean falling out of the sky?"
"No. Ankou's absence."
"That is true... Nowadays he keeps himself awfully quiet..."
"Yeah, and now's not the time to be quiet. This is a life or death situation and we need all the strength we can get!"
"What do you mean?"
"Ankou has been hiding crucial information about himself."
"Like what?"
"His second name..."
"Huh?"
"(Y/N), think back to other Bankai's you've seen, what is one thing they have that you don't?"
(Y/N): According to you.. A second name, but what does that mean-
...
...
...
(Y/N): Oh...
(Y/N) thought about how other shinigamis he's fought had another name for their bankai that was completely different from their shikai...
(Y/N)'s heard Ichigo's bankai name while he was training with him with the Vizards. Zangetsu was his Shikai's name but Tensa Zangetsu was his Bankai's name.
(Y/N)'s heard Renji's shikai name, Zabimaru, during their first encounter while he heard his Bankai, Hihio Zabimaru during their team up against Yylfordt during the arrancar invasion.
(Y/N) remember's Soi-Fon's Shikai quite well. Suzumebachi. And he just recently learned the name of her Bankai during their team up against Baraggan, Jakuhō Raikōben.
And upon recent battles, Gin's Shikai and Bankai. Shinso and Kamishini no Yari respectively.
Yet, here's (Y/N)... Without knowing the name of his Bankai...
"I never thought twice about why I never had a name for my Bankai... How was I able to use a Bankai without knowing the name?"
"It's because of Ankou's sneaky way of thinking. Remember his first introduction?"
(Flashback)
(Y/N): Are you my zanpakuto?
Ankou: Sure am. It's nice to meet you (Y/N). My name is Ankou, also known as the Grim Reaper.
(Flashback End)
"He introduced himself by two names..."
"He gave you the names Ankou and Grim Reaper."
"I guess giving me the name "Grim Reaper" was his way of bypassing the Bankai name requirement..."
"I'm no zanpakuto spirit but I can only assume that as long as the spirit in question gives the user some sort of name, they can achieve Bankai, no matter if it's a real name or not. However what I do know is that giving a false name doesn't bring out the true power of a Zanpakuto. I guess giving you two different names means that you would subconsciously associate "Grim Reaper" with Bankai since you were already used to calling him Ankou as your shikai command."
"But what does Ankou gain by keeping his name a secret?"
"Nothing... The question is, why did he choose to limit your power by not giving you his true name. And I'm going to find out."
" Hold on. You know where he is?"
"Where else could he go but the palace. Now let's go."
(Y/N), followed Thanatos inside the palace.
"You know, when I came here to learn resurreccion, I didn't think I'd be coming here to also learn about my Shinigami powers..."
Both (Y/N) and Thanatos made their way towards the throne room of the palace and as they got there, they were made face to face with a new face sitting on the throne.
Thanatos: You made yourself pretty comfortable up there, Ankou. Actually that's not your name in this form, huh?
???: So you've figured it out, huh?
(Y/N): You're kidding me... right? Where's the funny skeleton guy? He's not even the same guy!
Thanatos: So... wanna introduce yourself?
???: I'm simply the Grim Reaper-
Thanatos: Enough with your enigmatic act! We're both in danger if (Y/N) doesn't reach his full power!
??? got off of his throne, weapon in hand.
???: Giving (Y/N) my true name may lead him down a path he never intended...
(Y/N): What exactly does that mean?
???: The least information you have, the better...
Thanatos: If you won't play nice, then I'll just have to beat the answer out of you!
???: Let's not resort to violence now Thanatos...
??? snapped his figures and all of (Y/N)'s arrancars got up from their seats.
(Y/N) looked over to Thanatos.
(Y/N): he's not doing what I think he's doing... right?
Thanatos: *sign* You'll go this far? For what reason?
???: To protect (Y/N)'s morality. It's quite important to him and his journey...
Thanatos: It sounds to me you don't trust him enough!
(Y/N): It sounds like this power I'll get changes me...
???: No, the power itself doesn't change your personality... It's just... I don't want your outlook on the life around you to change...
Thanatos: Enough of your moral high ground! What (Y/N) does with his powers is his choice alone!
???: Hypocritical coming from the being who has taken over his body against his will.
Thanatos: I simply did what was necessary for (Y/N)'s survival.
???: Easy for you to say. You're simply in this for yourself. As long as your life is intact you don't care for anything else.
Thanatos: It seems words aren't getting through to you... Guess it's time for action.
??? signaled the arrancars and they teleported towards (Y/N), immediately pinning him down.
???: Sit this one out (Y/N)... We have some issues to work out...
Thanatos: Couldn't have said it better myself... Don't worry Overseer, I'll kick his ass so hard, he'll remember who's in charge.
(Y/N): How did we get to this point...
Thanatos and ??? stared each other down before charging into each other, clashing blades.
To be continued.
I've so glad this chapter is finally out. So far I've only seen one person realize that (Y/N) never had the name of his Bankai. It's been shown multiple times in Bleach that having either a false name or no name at all affects how powerful your Shikai and Bankai is. Yumichika and Renji are the two major examples of this.
Yumichika calls his Shikai by a false name on purpose as a way to insult his zanpakuto spirit and to keep his true powers hidden from his Squad. Renji legitimately didn't know the true name of his Bankai until the TYBW. Both have shown that using the true name of their Shikai and Bankai either makes their abilities stronger or straight up gives them a new ability.
Another thing to talk about is the second form of Ankou and (Y/N)'s hollow powers. As shown with Ichigo, going into your inner world in Bankai actually changes the form of your zanpakuto spirit and Hollow. White (Zangetsu) transformed into Ichigo's Vasto Lorde form while Old Man Zangetsu (Yhwach) transformed into his younger form. The same applies here. Hollow (Y/N) transformed into his Vasto Lorde form, now known as Thanatos, which is also the name of his resurreccion. Ankou now looks more Human and now Thanatos is trying to get Ankou's Bankai name out of him.
Also to address the falling Sky palace in (Y/N)'s inner world. The inner world reflects the individual's mental state. Same thing happened in Ichigo's Inner world. Ichigo's hopelessness in his encounter with Aizen reflected in his inner world by flooding the skyscraper city while he was training for the Final Getsuga Tensho. In this case, (Y/N)'s sky palace is falling out of the sky because he's really stressed out and desperate to find power that could compete with Aizen's.
And finally... The arrancars versus Vasto Lorde (Y/N) in the real world. I didn't get to write the Vasto Lorde Ichigo vs Ulquiorra fight so this is makes up for it. I just want you all to know that i had a hell of a time writing these next few fights coming up. Look forward to it.