first thing first I Do not own AT characters and This is my first attempt to write a fanfic Please review and if you guys like it I might post new chapters after a week or so.
At the border of the Ice kingdom and the grasslands
It's finally happening, a final showdown with the lich. Finn pinning down the last of the lich's goo monsters. "Be careful, Finn they might be dumb but they're incredibly strong", this is what PB said to him before confronting the lich and his army. "Don't worry Finn we got your back." Marceline the vampire queen said while tugging Simon with her, Simon was back without the influence of the crown but he retained its power. After destroying the goo Finn looked at his surrounding, "So much destruction" he thought to himself, this pushed his anger even more. With his signal he, Jake, Marceline and Simon attacked the lich, there were clashes of Finn's sword and the Eich's own hand, while Jake is providing Finn help with dodging strikes from the lich Marceline is trying her best to flank the evil being from behind. Failing to do it she was almost hit by the Lich's green flame but was saved by Simon providing an ice shield. After almost half an hour fighting, Finn had an opening and slashed down the lich. With all four of them charging towards their staggered enemy, they thought that this ends now.
But the lich had something up his sleeves. He held in his hands a time dilation device, with it he has one chance to slow down everything in the universe except its user for twenty seconds. After using the device he attacked all four of them and grabbed Finn by the neck. Twenty seconds has passed and the three helping Finn were shocked to see the lich strangling Finn. "Good bye hero." With those words departing the lich he stabbed Finn with Finn's own grass sword infused with the lich's green flames. After snapping out of it, Jake quickly grabbed Finn and the Simon imprisoned the lich within a sphere of ice, Marceline swings her axe and destroys the ice seemingly also crushing the lich. "Come on bro, don't die on me now"! Jake exclaims. "Quick! lets go to the candy kingdom." Simon said. And with that they flew towards the hospital inside candy kingdom. "Nurse! Nurse! We need help!" upon hearing nurse poundcake and doctor princess rushed to the scene. "Step aside, we need to examine him inside the emergency room." After laying Finn down a bed the trio with him are asked to return outside and wait for results.
"Oh Glob what's going to happen to Finn, will he be okay?" Jake asking himself while pacing pack and forth in front of Marceline and Simon. Suddenly princess bubblegum arrived, "what happened!?" she asked. All of them began rambling trying to explain what happened. The noise was only subdued when they heard the doors of the emergency room opened. "Were sorry Jake, we can't save him." all four gasped and doctor princess further explained, "we tried our best but the sword that is used to stab him had magic which almost completely destroyed his vital organs, we got him some minutes left but that's the best we could do." After hearing this they all rushed to Finn's side crying. "did we win," Finn asked. "We did hero" Marceline says while wiping tears of her face, Simon: "But he got you, Finn I'm so sorry I couldn't save you". Finn: "Yeah I know, I can feel it slowly dragging me to sleep." Jake hearing this bursts and hugs Finn, "No man you're gonna go through it you, need to." Finn tries to stop jake's crying, "don't worry jake I'll always look after everyone I'll only be gone physically but you know I will never be gone as long as I'm in your hearts." Finn turns and sees Simon, Marcy and PB, they still don't believe that he's dying. With his last breath he says "you guys be happy we'll see each other when the right time comes and also tell flame Princess I still love her." After saying his last word the last human in Ooo closes his eyes and everyone in the room cried much harder.
After 2 Days
"Is that all princess"? Asked peppermint butler, preparing the device which connects all kingdoms through a live feed. "Yes, that is all please turn it on." And with that all royalties from all kingdoms of Ooo flashed through the screen except the fire kingdom which is represented by one of their diplomats. "The queen delivers her apologies; she explained that she has more pressing matters to attend inside the kingdom." PB seemed irritated with flame princess' lack of interest with the meeting but she proceeds anyway."I won't beat around the bush since it's a serious subject matter." All beings on the screen had worried faces and tried their best to keep calm on what the princess is going to say. "Finn the Human is dead." "What!" everyone said in unison. "He fought the lich, they defeated him but Finn was fatally wounded and died in the candy kingdom hospital." All of them were crying after hearing about the hero's demise but the feed from the Fire kingdom was cut off.
Fire kingdom
The diplomat was shaking as Flame princess destroyed the device in front of him, she was watching the whole time, wearing a face of disbelief and anger. "She's lying! Why would she say that!?" Cinnamon bun is trying to calm her down. "maybe she's telling the truth, the princess is not the type to joke about death." "I'll see to it myself." And with that the enraged princess zoomed out toward the candy kingdom. "There she goes, rushing with emotions again." After expressing himself cinnamon bun dismissed the scared diplomat. Last time finn visited the fire kingdom cinnamon bun was keeping him from meeting with Flame princess. "please CB let me see her." "No Finn, She needs more time, she's still devastated by what you did to her. I want to protect her, become the father she never had." With that the human bowed in front of him and asks his forgiveness for intruding and went back to the grasslands. "Oh man Finn I never thought you would check out this early. What will happen to Ooo now?"
Candy kingdom
"That is all we expect each of you tomorrow at the funeral." Slowly turning off their live feed, princess bubblegum started doing preparation for tomorrow's sorrowful event. "Peppermint butler you are in charge with the place where finn's body will be placed and root beer guy prepare the banana guards and secure the kingdom, we might have more people visiting than we expect so you are in charge with controlling the crowd if it gets messy." Both castle staff received their orders, bowed towards the princess and started with the preparations. PB was emotionally exhausted with these events while walking towards her royal quarters she smelled something burnt. "I thought you have more important matters to attend to?" she instantly knew it was flame princess. "I always knew you were a liar but how dare you say that Finn is dead." "you think I'm lying? Finn still loves you but you didn't even bother to hear him out, did you even know what he had gone through when you left him, he was torn into pieces, but when the lich resurfaced the first being he worried about is you! Come with me!" she dragged her to the garden at the back of the palace and showed the grieving dog with Marceline and Simon. "come on Jake stop crying what will… What is she doing here?" as soon as flame princess saw the hero's dead body lying in a bed of flowers she broke down. "how is this possible? I never thought that he would actually…" she stops mid-sentence and starts crying hard while starting to burn a bit brighter with anger. "Yeah, that's right he's dead. I don't know what he saw in you, he was trying to win you back, but you pushed him aside, did you know that he thought about your safety when the lich resurfaced himself." Marceline continued telling FP everything Finn did for her while she were too busy with the fire kingdom. Simon saw that Marceline was starting to cry and rushed to the weeping vampire's side to comfort her.
Meanwhile…
Finn quickly opened his eyes observing his whereabouts "this place again." he ventured out the devastated landscape covered with rubbles of cars and old buildings. Finn recognized the debris as Pre-mushroom war objects; he saw them back at the library. "I wish today this place is clear of…" he was interrupted by the sound of bones clanging with each other, after hearing this he knew what to do. He prepares himself and tried to pull out his sword only to find that it's gone. With that he began running towards the shining castle in the distance. " Glob dammit! I gotta lose these dudes!" struggling to climb the mountain of destroyed buildings he stops at the top and finds that the skeletons can't climb releasing a sigh of relief he slides down on the other side in front of the river of forgetfulness. "All this running makes me thirsty." Leaning to take a drink he remembered something that happened when he first visited the place. "How could I forget that, Jake almost lost his memories forever after drinking this water! Man this river is so effective it induces slight memory loss just by approaching it." After walking around the river he found himself at the entrance of Death's zen garden. As he enter he saw the silhouette of the man wearing a gray hat watching the events happening at Ooo from a big screen. "still making women cry even in the afterlife. I know this is obvious but those three girls really liked you." Finn approaches the being, saying: "I have no idea what you're talking about." Death laughs "well think what you want and hey welcome back to the thirty-seventh dead world. Finn the human."