Disclaimer:I don't own Adventure time, it's characters, or most of the songs I use. Only what I make.
Chapter 1
The Mysterious Man

Finn walked from a cave into the dull light of Twilight, gazing up at the amber sky. His shoulder length blonde hair was a messy mop, he wore a pair of tan hiking boots, a pair of kaki cargo pants, and a light blue shirt under a dark navy blue jean jacket. Out next to him stepped the radical undead queen he loved so much, her long, raven black hair in a single braid down her back, reaching just below her shoulder blades. She wore a grey, sleeveless tank top, a pair of short jean shorts, and a pair of crimson, mid-calf high hiking boots. She looked up slightly as she turned her head to look at her handsome boyfriend. He'd grown a lot in the five-ish years she had known him. She smiled at him as he took a deep breath, "You ready for one hell-of-a night Marcy? It's gonna be interesting..I can feel it.."
She chuckled, "Okay Hero..where first?"
He smirked, "Well..I think.." His eyes suddenly locked in one direction as a dark figure burst from the foliage of the great forest that bordered the eastern and southern sides of the grasslands just a few hundred yards away from them at full sprint. Suddenly a black and grey streak shot from the tree-line and struck the figure in the back, causing it to fall to the ground, "We'll start with that..come on.." As he started running towards the figure, Marceline following. He was about fourty-ish yards from the figure when a few other figures emerged from the tree-line. He could see the three figures were Umbranic Assassins. Finn skidded to a halt between the fallen figure and the onyx skinned assassins, his white bladed long-sword drawn and held in a defensive stance.
The middle one spoke in a deep, raspy voice, "Move out of our way boy..this does not cconcern you.."
Finn held his ground with a smirk, "I fight evil beings..and as far as I know..The Umbranic are made of pure evil..so no.."
The dark being chuckled hoarsely, "So be it..prepare to die hero…" and the being charged at Finn, swiping at him with a dark blade. Finn parried the strike with ease and Kicked him back, finding his friends were gone, replaced with two piles of ash.
The being smirked beneath his mask as his head cocked slightly to the side, as if listening to some unheard voice, "You're time will come hero..I would end you..but my master beckons me..untill next time.." and the dark creature disappeared in a wisp of black smoke. Finn looked around swiftly and sheathed his blade before turning towards the figure, crouching next to it and doing his best to turn the remarkably heavy being over onto its back.
Marceline appeared next to Finn, gazing at the being, "It's alive..it's heart's still beating…barely.." her voice lined with her curiosity.
Finn looked at her, "What is it?"
"It..I don't know what it is.." she replied to him honestly.
"Well whatever it is it needs help.."He pulled his new crimson red single strap backpack off and started looking through it.
"What are you doing?"she inquired.
He pulled out an intricately designed, light blue vial, about five inches long and one-and-a-half inches in diameter, "Cyclops tears..they can heal any wound.." he held the vial over its face, tilting it, causing one drop to fall onto the being's lips before putting it away and putting his pack back on his back, "We need to get it somewhere safe while the tears work their magic.."
"What about the Treefort?" she suggested.
"Good idea..Jake did some renovations to reinforce it too..but I think you need to carry it.."he smiled.
"Okay..oh..I've been working on my magic..let me see if I can teleport us there.."her face contorted in concentration before a sudden change of scenery and Jake's patented shriek of terror is heard.
Jake sat on the couch clutching his fury chest as he stared at the his adopted brother and the vampire queen in terror, breathing heavily, "WHAT THE GLOB YOU GUYS! You almost gave me a heart attack.."
Marceline dropped to a knee, her breathing tired and labored, and Finn tried his best to say something but ended up sprinting to the bathroom and puking his guts out. After a few minutes Finn walks back into the living room holding his stomach as Marceline stood, "Oh glob..That was draining..you okay Finn?"
He looked at her, "Yeah..I lost my lunch but Im fine.."
She smiled, "Where is your guest room?"
Finn pointed and Marceline carried it to the room, placing it on the bed before walking back out.
Jake raised a brow, "Who was that?"
Finn took his bag and sword off his back and sat next to his brother, "Dunno..we saved him from a few Umbranic Assassins.."
"Wow..Um..well..I have a date with Lady tonight.."Jake said as he stood, "So I guess I'll see you later.."And he grabbed his bag and left.
Finn sighed as he leaned his head back, looking up at the ceiling. Seconds later he heard Marceline tuning up her bass, "Wanna have a little jam session Finny?"
He looked at her and smiled, "Sure Marcy.."he stood up as she began recording.
On the ground I lay

Motionless in pain

I can see my life flashing before my eyes

Did I fall asleep?

Is this all a dream

Wake me up, I'm living a nightmare

I will not die (I will not die)

I will survive

I will not die, I'll wait here for you

I feel alive, when you're beside me

I will not die, I'll wait here for you

In my time of dying

On this bed I lay

Losing everything

I can see my life passing me by

Was it all too much

Or just not enough

Wake me up, I'm living a nightmare

I will not die (I will not die)

I will survive

I will not die, I'll wait here for you

I feel alive, when you're beside me

I will not die, I'll wait here for you

In my time of dying

I will not die, I'll wait here for you

I feel alive, when you're beside me

I will not die, I'll wait here for you

In my time of dying

I will not die, I'll wait here for you finished

I will not die, when you're beside me

I will not die, I'll wait here for you

In my time of dying..
They sang a few more songs before heading to bed, enjoying a bit of fun.