It's a little rough but here goes
Enter, a scene of Eris, Roxy, Sylphie alone together. They're discussing surprise gifts each of them have for Rudeus as celebration for winning the final mission or whateve
Eris starts talking about how she can't wait for Rudy to get home as it's her turn and they haven't done it in ages because of all the battles
"Eris... you know... don't you think we should make tonight even more special for Rudy?" said Sylphie
"Like how? Our gifts are already really good." said Eris quizzically
"Well, I know it's your turn tonight but me, Roxy, and Elinalise were talking and she taught us something men REALLY like."
"O-oh, you want to have... one of t-those" said Eris, bright red, fidgeting "GAHHH it's sounds so **embarrassing** though.
"Please Eris? I *know* Rudy has been dreaming about the day we let him. Let's surprise him and make him a happy man tonight.
"Arggh" Eris fumed, then sighed "FINE, but it sounds hard. How do I... uh we do it?"
"It's not just the foursome" Roxy chimed in "Lise taught us, well, a few tricks to get Rudeus... *extremely* excited."
"L-like what?"
"You just leave that to us." said Sylphie softly "After our little private meal and gifts, you whisper in Rudy's ear that you want to try switching roles tonight and challenge him to show you how much of a man he really is. Teehee I know that'll really get him going. Then go to his room and wait."
"Ok."
"Before that, I'll yawn and say I'm beat and pretend to go to my room to sleep." said Roxy
"I'll take Rudeus aside and tell him I hid a bottle of aphrodisiac spiked wine in the basement, and that Eris hasn't had a turn in forever so he should use it to keep up.
That'll be a lie, it's just regular wine. I have 4 bottles of the pure stuff in my room." said Sylphie in the exaggerated candor of a villain.
"Right" Eris said, her embarrassment giving way a bit to some excitement. This sounded almost like a battle plan.
"I'll say I'm going to help Lilia clean up, but after he goes down I'll sneak into his room with Roxy and join you."
"Gotcha, and then we wait?"
"Well not quite, we want Rudy to think he walked into heaven when he sees us."
"What does that mean?"
"We'll show you, just follow our lead. Promise me ok Eris? No running away. No getting embarrassed"
"Of course!"
"Well" said Roxy slyly "looking embarrassed is fine, Rudy'll like that. Wait what if *Rudy* tries to bring up the foursome at somepoint?" said Roxy suddenly
"I planned for that, I'll steer him away from it. 'Eris has been waiting' ect ect." replied Sylphie
"Oh Rudy..." murmured Roxy wistfully
"Allright team Greyrat, remember what we rehearsed, meeting adjourned!"
"Right!" said Eris and Roxy together

[Perspective switch]
Rudeus arrives
"Surprise Rudeus!" my three wives announced. A full dinner table already prepared
"Haha what is this dears?"
"Oh just a little miniature victory dinner. Before the big party with everyone in a few days." said Sylphie, beaming.
We eat, chat and they surprise me with lovely gifts.
*Eris sure looks jittery, ah she must be chomping at the bit; it's been quite a while since her turn. Oh she's going to destroy me tonight.* I thought in faux resignation.
Roxy yawns. "Gosh I'm exhausted, I'm going to turn in early. Goodnight Rudy, everyone."
"Ah, goodnight Roxy"
"Ah Lilia let me help you with the dishes" offered Sylphie
Eris called over to me "Lets hurry up and go upstairs. I've been waiting forever"
*Rest in peace my hips*
Eris suddenly leans closer "S-say Rudeus how about we switch positions tonight?" said Eris in a softer voice. Then summoning confidence "It's high time you showed me how much a man you really are!" she stated playfully as she started up the stairs, though also beet-red.
That lit a fire in me, and I was already on the first step before Sylphie hastily called to me. "Hold your horses mister can you give me a hand in here first?"
"Sure honey" I said startled.
Once in the kitchen Sylphie looked over to me with a mischievous expression.
"Err Sylphie what do you want me do in-" I inquired.
"Rudy theres a bottle of wine in the basement Elinalise gave me. It's infused with a little aphrodisiac, share some with Eris so you can, heh, entertain her well." said Sylphie winking.
*Oh what did I do to deserve this angelic being?*
I grabbed her into a rough affectionate hug and nibbled her ear.
"Oh just wait till I use it on YOU" I cackled evily.
"Eee oh I just can't wait" she replied "but unfortunately Eris is at her wit's end so I'll have to wait"
After a little more banter Rudeus heads toward the basement door.

[Wives]
Sylphie is halfway up the stairs before Rudeus is even at the basement door. She gives Roxy's door a knock and they're shortly in Rudeus' room with Eris. The three of them in erotic nightgowns.
"So what was this trick you were-" Eris started before Sylphie cut her off
"Think fast girls, Rudy will be up here before long and we are going set the perfect stage. Down your bottle girls."
"Right" nodded Eris.
"Yes, ma'am" quipped Roxy.
"Eris you're tall so sit on the edge of the bed, here's the trick." 
Obliging Eris had barely seated herself before Sylphie had strolled over and boldly took Eris's lips into a deep kiss. 
Yelping Eris reactively pushed her away "S-s-sylphie what are you-" 
Drapping her arms over Eris's shoulders she softly but urgently replied "Shhshhshhhhhh remember your promise Eris, just relax and stay still. We want Rudy to see heaven when he opens that door. Elinalise tells me men lose their minds when they see this. Roxy you're up."
"Ma'am yes ma'am" giggled Roxy nervously
Roxy kneeled down and placed her hands on Eris's hips and deftly unlaced her panties.
"Eep" said Eris biting a finger.
Working quickly Roxy then parted Eris's legs gently.
And then her head went between them.
"ROXY?!" Eris screamed, Sylphie already having stifled her mouth with a hand, knowing.
Firmly grabing Eris's wrists Sylphie cooed gently "Don't fidget now Eris, this is just a practice demonstration. The second we hear Rudy on those steps; we're both going to town on you. Give a bit of tongue back Eris, you're a dead fish right now."
"And ease up on the vicegrip woman." Roxy chimed in gruffly, taking a breath.
"Eris squirmed futiley, her body growing hot, the aphrodisiac kicking in
Moments after, hear Rudy on those steps they did.

[Rudeus]
*I come to slay a dragon this night*
I'm practically vibrating with excitement as I ascend the stairs, bottle and cups in hand.
*Lilia certainly took her time getting me these damn glasses. I've got places to be lady!*
Shrugging I open the door
"Ohhoho Eris I hope you're ready, this wine has-"
My body, my mind, my very being comes to a screeching halt.
A shattering sound fills the room. The bottle having slipped from my hand and tumbled upon the floor.
I am in presence of a holy ritual.
The bearers of the 3 Great Holy Relics before me are responding to the prayer I had just given to the Great Holy Shrine upon retrieving the wine.
Though I had only addressed the one, all three had chosen to grace me with their magnanimity tonight.
I fell to my knees, trembling
My white haired goddess was, as if in ravenous hunger, devouring the tongue of my red haired goddess. Who shuddered and meekly returned the affections offered.
My gaze drifted down.
My blue haired goddess was similarly occupied, her head bobbing as she busied herself with her holy task.
"Oh," said my blue wife, as if just noticing me. As the white and blue both parted from the red, the latter moaning and gasping. Two thin strings of spit still connecting the three to each other. "look who it is."
I gazed in awe at my wives, an atypical expression on the faces of all three.
On Sylphie's face an devilishly bold and assertive one.
On Roxy's a hungry and drunken one
On Eris's a meek, shy, and delicate one
"You kept us waiting dear, we want to give you your real present. Look." said Sylphie in the most seductive voice I had ever heard in my life, holding an ornate bottle. It's 3 empty sisters on the floor nearby.
"R-Rudeus" gasped Eris her face beet-red.
The second I heard that all thoughts save one left my head, and before I knew it I was barreling full speed towards the bed, all but tackling my wives and dragging them further into bed.

FIN