Bonded Tentaculum
A tree of great size stood entangled in dark green vines. They were black, dark as the night. It coiled and choked the life of such a beautiful tree. Thick spikes continued to tighten, making it groan and creak. The magnificent thing was suffering, trying to hold onto the life it once had. The darkness almost shrouded the entire thing into a blunt nightmare. The shadowed cave blocked the light away, but a thread of it landed on a dark blue alicorn, calling out...
"Sister... Sister..." the alicorn called out, "Are you alright?"
An unconscious white alicorn murmured, before two royal eyes opened. Her vision blurry and struggling to adjust to the darkness.
"Luna?" the white alicorn whispered, "Is that you?"
"Big Sister! I am glad you're fine!" a dark blue alicorn replied as a large vine brushed past her coat. She almost screamed, feeling the unknown texture against her. Her hooves were stuck to the ground by an alien stone. Embedded into the ground, Princess Luna titled her body to the side as the plant creaked.
“My… these things…” Luna whispered towards her older sister, Princess Celestia, “What do you think they are?” The tentacle that touched her ignored her and made its way out of the cave.
Princess Luna’s dark mane waved in the air despite not being in any wind. She made an effort not to attract the plants and crept low.
“I don’t have the slightest clue, Luna,” Celestia said softly, watching the giant tree nearby them being entangled, “The Tree of Harmony lost its magic and increased the growth of the Everfree Forest…”
“And right before the Summer Sun Celebration too!” Luna whispered, wanting to keep her voice low, “I hope we can find a way to escape!”
“Have you tried magic?” Princess Celestia asked, standing up straight and tall. Her eyes looked down at the prison and stared at it curiously.
“No, not yet,” Luna replied back, looking uneasily at the other plants continuing to grow at an exponential rate, “I wanted to wake you first before we tried anything.”
“Well, these organisms seemed to be drawn in towards light,” Celestia replied back, her multi-color mane also flowing without any assistance by the wind. “Look at that.” she said, motioning her head towards the mouth of the cave.
Multiple rows of the plants made a chaotic structure right above it, continuing to grow and creak with each passing second.
“I hope these plants aren’t attracted to magic then,” Luna whispered, her horn glowing in an ominous light, “I don’t want-”
A large tentacle immediately brushed past her horn, cutting off the light emitted by it.
“Curses!!” Luna said loudly, cursing beneath her breath. She clamped her mouth shut, just as Celestia’s horn was also negated of magic. Celestia tsked, trying to conjure up any kind of magic to assist in their escape.
All the vines ignored them, despite Luna’s yell. Her voice echoed throughout the cave and halted all the progress of the plants. They seemed to stop squirming, ceasing all activity. Silence claimed the cave, only the shallow breaths of the two princesses emitted any sound. A drop of water from above came down in a rhythm. It continued with a plip until two different tentacles from the opposite side of the cave slowly went towards them.
“Keep still, sister!” Celestia hushed, staring intently at the approaching plant. Luna nodded, staring at the incoming plant.
The one on Luna’s side slithered up to her, stroking gently on her muzzle. Celestia’s did the same, their tips softly rubbing their muzzles.
“Are they… friendly?” Luna whispered, watching her tentacle starting to get to Celestia.
“I think so.” Celestia replied, looking at Luna’s plant slowly coming in at a wave-like motion. “I hope so…”
Celestia’s plant went towards Luna, who had fear in her eyes. She however kept her composure as the tentacle patted her on the head. It gently took her crown, putting a smile on Luna’s face. Celestia’s new pal also did the same, taking her crown.
“I think they just want to play.” Celestia said, sighing in relief. Luna softly giggled, looking at the plant twirl her crown with expertise. Celestia observed them, not knowing her tentacle was going near her rear.
A sudden sound of tissue squishing made Celestia yell in surprise, making her knees buckle. Her tentacle penetrated her, going in and out of her vagina with a wet sloshing sound. She screamed and groaned, unable to escape the relentless tentacle.
“Sister!!” Luna yelled out, she was however cut off by a loud clatter of her crown and was met by the tentacle. It went deep inside her mouth, making her cheeks bulge from the enormous tentacle. Her eyes teared up, as the tentacle went deep down her throat. Her screams were muffled while Celestia was screaming out. Celestia bit her bottom lip as the dark green tentacle continued to pump in and out of her. A few tears from her eyes merged in with the sweat, making her only unleash a moan from her mouth. Her eyes were clearly in pleasure, taking in the whole tentacle inside of her.
“It’s so hard…” Celestia thought as unbelievable pleasure shot through her body.
Her tongue was out, taking deep breaths. Her pussy was getting railed at a solid rhythm. The momentum of the tentacle almost buckled the stone around her hooves, going in slowly, but very deep. Each inch that went inside her made her hungry for more. She felt her mind cloud up and felt the tip in her womb.
Luna was shrieking, but her voice could be carried so far. Her lips were stretched as far as they could go. Her eyes widened, grunting every time as the tentacle went in and out.
“P-Please!! Luna screamed internally, “Make it stop!!”
Her marehood was pouring out her own juices, her leg twitching from the feeling of the tentacle. Her moans continued on, another tentacle coming in to her wet pussy. The tip of it slowly circled the outside part of her vagina and then rubbed her clitoris. Her moans intensified and turned into a scream as the tentacle penetrated deep inside of her. Luna’s eyes brought forth tears, trickling down her face. She closed her eyes as her mouth kept up with the rampaging tentacle and also began to feel it pump in the back. Her tight hole made an extraordinary sound with the tentacle, the wet sound and muffled screaming coming out of her.
The white regal princess suddenly felt tentacles near her wings, which was sprouted up from her resting position. The rocks at her hooves were shattered into many pieces, making an opportunity for four tentacles. They grabbed each leg and holstered her up while a giant one crept to her face. Celestia was raised up higher in the cave, getting off of the ground. She reluctantly opened her mouth, her lips were unsure, but her tongue was wild and crazy. A giant tentacle came towards her begging mouth, in which Celestia lips puckered up and began to suck on it. Her tongue tasted plant matter and saltiness before the whole thing was taken down her throat. She moaned, feeling her full weight sit on top of the tentacle in her marehood while taking it deep in her mouth. Her lips slid across the wide and choked a couple time. Breathing through her nose, her front hooves held onto the monstrous tentacle.
Luna below also become lifted up by tentacles. Her nice ass was taking it deep, making her vaginal juices splash everywhere. She struggled to get everything out, her hooves flared everywhere but was captured and held by dozen of tentacles, Her teared eyes closed, feeling the burning passion inside her began to ignite. The place between her legs was getting hotter and hotter, the same thing with the color on her face. A bright crimson on her face grew, feeling the juicy tentacle go deep inside for for each moment passing. The thing in her throat was now as if it was going down her esophagus. A soft moan escaped from her lips, feeling her insides spread out wide. The large bulge from the tentacle left her squirming around, making the tentacle drive even deeper than before.
Both the sisters were starting to reach their climax, the squishing intensifying from the tentacles at an accelerated pace. The rhythm began to go faster and faster, they went in deeper and deeper. Celestia’s eyes almost went in the back of her head, and the same thing with Luna’s. With an immediate burst, the tentacles went deep as they got possibly go and unleashed a monstrous load. The liquids filled up Celestia and Luna with the hot and sticky liquid. Their mouths and pussies exploded with the white material, with too much they can handle. Deep heated pleasure overcame their bodies, unable to breath with the cum inside them. The two slowly closed their eyes from the lack of oxygen and slowly drifted to a deep sleep. The tentacles left the holes, letting drizzles of semen slowly ooze out. Their mouths were soon left, allowing them to breathe. A black magical casing soon covered them, leaving them in the scent of the thick sticky liquid. Their eyes closed to rest, not knowing when they’re going to wake up.
Author's Note
I sowwies. 
I just couldn't resist!! 
If you're wondering why only two got some fun, it's because they were the seeds that touched the princesses in the Discord flashback. It touched them in the muzzle, making some 'impossible' bond. Does it work? It does to me. They got extra tentacles due to being a few of the first being planted. All the tentacles on each princess was the same, coming from the same seed.
And with 'Rape', sure they were taken advantage of. But nonetheless, they enjoyed it. Well... Er. Yeah, it was rape.
I also wrote this while listening to Two Steps from Hell's: Strength of a Thousand Men at 1.5 speed. It was very interesting and also awesome in a way.
Ah.
Well.
That's a good start with Season 4. Don't cha' say?
