Disclaimer I do not own Hazbin hotel/helluva boss series, and I am not making any money by writing this story. Hope everyone that reads this enjoys it.
thoughts will be in italics

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The last few years had been rather successful as Purgatory had worked as intended on her end, greatly slowing down the growth of hells population as portions of souls that would've gone to hell ended up here. She did feel a bit miffed that about how she couldn't really take part in the exterminations anymore with her new job, but she still enjoyed that she had been trusted enough for such an important responsibility. Lute also knew that Sera was quite happy with the realm as while not in large amounts souls had started arriving at the gates that had gone through the process of starting over in Purgatory.
If she was being honest with herself Lute hadn't thought there was real chance at a soul redeeming itself and yet it had been a pleasant surprise when she had seen the first soul leave the realm for Heaven.

Patrolling the new realm was a big job but she felt it was worth the effort knowing that it was working as Heaven intended. While a soul redeeming an ascending had been a surprise for Lute what had been more of a conundrum for her to figure out why Adam had been so focused on setting this whole thing up. He enjoyed the exterminations just as much as she did and while she didn't mind not really taking part anymore, she couldn't fathom the idea of Adam giving up the chance to punish his descendants that became failures and fell. And as much as she like hanging out with him she knew him well enough to know that he tended to be rather lazy at times unless he found something fun enough to put effort into but this, Purgatory didn't sound like fun, it was just a ton of work with a big chance that it could've been a failure. No, no trying to understand how Adam thinks and does what he does is a bad idea. Especially after he dragged me to that after party from the thousandth extermination. Lute shuddered as she shoved the memories of that day deep down into her subconscious and decided to go flying to clear her mind, maybe doing some work would help her think of something else to focus on with all her new free time.
Flying around to get a better look around to make sure the barriers separating the realm from most of the rest of creation where still in working order Lute felt something off in the energy of the realm, like it was being thrown off balance. She stopped as she tried to figure out what was going on. None of the barriers were damaged and she hadn't been sent any messages from Adam or Sera, so this wasn't Heaven. Lute rushed down to the surface of the realm to try and figure out what she was sensing but was shocked at the sight in front of her as she reached the surface of the land. Wait, it isn't just going off balance. Its gathering and coalescing. What in the fiery pits is going on?
A truly giant tree like growth had sprung up seemingly out of nowhere. It's roots spreading far and deep and its branches reach out in all directions. It would've been majestic in a certain sense if not for the clearly demonic nature of the tree as eyes seemed to be growing all over its trunk and mouths filled with sharp teeth at the ends of its branches and the tips of roots that broke through the surface of the land. The sight of such a monstrous creature that shouldn't even be in this world froze Lute into in-action as she watched the thing simply spread out its branches and roots.
She forced herself to act when she was broken out of her stupor by the sound of screams. The voices of terrified souls running for their lives, begging for mercy as the tree began tearing into the city closest to it. It's roots and branches devouring anyone they could reach and grab. They aren't rising or falling… ITS STEALING THEIR SOULS! Rage filled Lute as she went in for the kill. These souls had been given a second chance by Heaven and they were still being tested, they were innocent souls, and this thing was devouring them as if they were just finger food snacks. These souls still had a journey to go on and she would not allow it to be cut short.
A blast of divine energy tore the clouds in the sky apart as the people looked up in terror wondering if another new horror had arrived, instead they felt a sense of calm and safety as a lance of golden energy slammed into the tree tearing off a few branches as people scrambled to escape or to help those trapped in the grips of the cut of branches.
An unearthly scream came out of the trees many mouths as it experienced pain for the first time. Rage engulfed it as its many eyes seemed to swim around its body to find the source of the new feeling. They stopped looking up in the sky at the flying figure. Dozens of roots shot up out of the ground though none of them managed to reach the target as she dipped and dived and dammed around the attacks and with each miss another branch or root was cut clean off leading to more pain and making the tree even angrier.
Lute was unsure of herself for the first time in centuries. She had taken part in many exterminations and had slain some of the most powerful sinner's hell had seen and yet this tree felt off, different to the demons and sinners of hell even though she could sense that its power was similar. She was definitely hurting it, and it seemed to be weakening and slowing down the more she injured it but unlike with sinners or hell-born her holy energy didn't seem to nullify the creature's power at all. "What in the high heavens and low hells is this thing?" Such a creature shouldn't exist in this realm at all, it puzzled Lute that she had no idea what she was fighting or if she could even kill it, heck she wasn't even sure where to hit the tree in what could be considered its heart.
It was just a moment, but the tree saw that the winged being was distracted. A lone root went as deep as it could reach while the tree sent as many branches and roots at the thing to keep it distracted.
Success, while the frontal assault had been evaded or destroyed the being had not noticed the sneak attack as it was caught by surprise as the lone root erupted right underneath it dragging it down to the drown and while it was stunned from the impact more and more roots worked to pin the thing down, causing building to collapse on it and then dragging it as deep into the ground as possible where it's roots held the advantage.
She had gotten careless and distracted and now she was paying for it. The fall hadn't hurt to badly but each time she was forced to block a strike from the roots or was unable to fully evade them in the mess of underground tunnels the roots of the tree had made she could feel herself slowing down as her stamina and strength were fading. How is this thing hurting me? Why am I struggling so much with this? Could I lose? Am I going to fail these souls and my duty to this realm? Am I going to fail Heaven's mandate? For an angel Lute was rather prideful but even she knew that this was not going her way, she needed to call for help. At first, she thought about calling Sera for help but decided against it. While she respected the high seraph, she knew her well enough to know that whatever had happened here would result in Sera simply shutting the project down and wiping the slate clean. Lute had seen enough progress to know that Purgatory had a real chance of success, and she wouldn't just give up on all the progress she had seen so she sent a call out to Adam.
"Sup Lute what's happening."
"Adam I don't have time to talk I need your help. Get to Purgatory as fast as possible!"
Adam joked a bit about Lute being bored and lonely, but she just yelled at him to get over and help her as she showed him an image of her situation. Adam spat out the drink he had been slurping on at seeing his friend in trouble.
In Purgatory the people felt fear griping their hearts as the angel that had come to save them seemed to have failed in her duty. The tree had gone back to feeding on whomever it could get into its mouths growing again as it fed on the people still left in the vicinity. It let out a ghastly laugh as whatever regular weapons the snacks had seemed to do no real damage at all, especially compared to the winged thing that had attacked it earlier and that would soon become another morsel for it to digest.
The ground and air seemed to vibrate as the sky grew bright once again. The tree started to feel frustrated at its mealtime once again being interrupted while many people were confused as they heard an odd cross between harp and guitar music fill the air. A Shockwave struck the area nearly uprooting the massive tree and all but guaranteeing tinnitus in the future of any of the survivors. "Epic entrance hell yeah!"
Another winged figure exited a massive golden portal as a second Shockwave though much more localized came out of his harp guitar utterly destroying the wall of roots and branches that had moved to attack it. "Well, this can't be good. Hey tree thing! Have you seen my partner? She's about this tall, a bit of an attitude, very serious and tends to always have a scowl on her face and was likely fighting you." All Adam got in return was a roar of hatred aimed at him as whip like leaves grew out of the tree lashing out at him. All of which he simply incinerated with a flash of his power.
"No need to be so rude dude." Adam laughed as he danced around the creature tearing out chunks from it as it tried to kill him. "Are you even trying to kill me. I've faced stomach aches more troublesome than you."
Despite its best efforts the tree couldn't land a blow on the new winged one. In its effort to kill the new arrival the tree had lost focus on its attempts to kill the first one as Lute managed to claw her way out of the underground when the roots had stopped attacking her.
"Nice to see you arrived on time for once sir." Gasped out as she worked to catch her breath and regain her bearings.
Adam gave Lute a thumbs up with a big smile though he took note that whatever this thing was it had managed to hurt her. He realised he would have to take this thing seriously in case it managed to hit him. "Well, it's been fun and games, but I think it's best we end this now. Hey lute hand me your spear will you."
With his partners spear in hand Adam flooded the thing with massive amounts of divine energy as he flung it into the air. For a moment nothing happened followed by the sound of thunder as like a bolt of lightning the spear fell out of the sky splitting the tree in half piercing all the way to its core as it was flooded with holy power.
"Well I think that solved things. You ok Lute and who was your new friend?"
Lute simply gave him a thumbs up as she took a chance to look herself over. "It was a bit tougher than I expected. Thanks for the assistance, sir. However, to be honest I have no idea what that thing was or where it came from but what do we do about all of this?" She motioned to the corpse of the tree and the massive amount of destruction.
Adam shrugged neither of them knew what had caused this to happen or really to fix the problem of the people here having actually seen a demon not to mention them having to reveal themselves to slay it. "Let's wait and see, let things play out for now but we can't let Sera find out about this. For now, let's get you cleaned up." As they left Adam took one last look at the fallen creature wondering why the tree looked and felt so familiar to him.
While for the angels the fight would slip from their minds for a while, things were different for the people of Purgatory. They had borne witness to a fight between a tree monster and angels. Their world had been changed forever in their minds and how it physically worked as people took note of odd changes in behaviour, scientists noticed a new form of energy flowing around the world and took note of new discoveries as they studied the spear left behind by the angels and the corpse of the tree. For them the world was changing and not for the better as people started to fall ill, as they started to change, and many began to wonder if hell had found its way to the surface and what that meant for the future.