The son of Lily and Snivilus.
That thought was painted on the face of Sirius as he sat there in his ancestral home, staring at the son of his best friends wife, and his nemesis was sitting right before him.
Cassius could only chuckle internally as he watched the struggle on the former prisoner of azkaban's face.
"I dont care about your relationship with my dad, i just wanted to help you out for my own sake."
Cassius readily admited.
"For your own sake...?"
Sirius looked confused as he heard this omission.
"Well its like this."
As Sirius sat there Cassius began to unravel the web of mysteries he'd concocted.
Most of what he said was true though some of the sources were changed to better fit the narrative.
He started off with his explaination of his growing up, first with what he was told by a nurse from St. Mungo's who come by out of guilt to check up on him in the muggle orphanage.
No such person existed of course, but it was better than explaining he was concious from birth which would be highly irregular.
Once he knew Lily potter was his father, the nurse also revealed that his mother had mentioned the name 'Severus' upon seeing his face, which through his research he'd found to most likely mean the potions master Severus Snape.
Sirius had Cassius stop his story here, mostly due to his anger having almost boiled over at this point.
The sweet caring Lily he knew, had not only had an affair behind James's back but then cast the resultant child away!
~
As Sirius retreated to the top floor sealing himself within his room, Cassius began to investigate the Black family home.
This was an ancient household of one of the sacred 28 families, but since the death of Regulus Black the house had been greatly neglected and left in a state of disrepair as the hundreds if not thousands of household enchantments began to fade or even contort.
For Cassius this would be a perfect training ground to test his growth in spell craft.
Using the staircase as a perfect example, he pulled out his primary wand, leveling it as he pointed to the stairs themselves.
"Reparo"
The cast was simple, but thanks to the charm having been raised to the third level already, the stairwell from the main floor to the 2nd floor was quickly adjusted returning to an almost like new state.
Well like new except for the fact it was still grungy and dirty as can be.
But that was solved with the wave of his wand once more
"Scourgify"
The spells quickly covered the stairwell and the dirty stains and build up began to fade away however thanks to the powerful wards protecting the home, so even a third level spell could not deal with the build up at once, but after a second, third, and finally fourth casting of the spell, the staircase was like a breath of fresh air compared to the rest of the house.
~
But Cassius was not content simply with playing house and cleaning up the Black house of Grimuld place, if Sirius was not around, well what better thing to do than to strike revenge on the man for his father, while at the same time claiming the title of maurader for himself whilst at it.
Thanks to future knowledge of the eventual conctions and spells created by George and Fred, Cassius was well primed to setup a prank war against Sirius.
One the old man would not be prepared for, but one he would get after being a lame duck for 10 years sitting in prison.
Traps were setup all over the house, tripwires, proximity charms... nothing none lethal of course but every single one of them would be a great, great annoyance to just about anyone.
Except... Cassius sorely underestimated the old man.
When he finally emerged from his room, having collected himself and changed into a new set of clothes, he climbed down the stairs only to setoff the first trap.
*Poof*
In an instant the clothes he was so proudly wearing had been transformed into a pink and blue miniskirt outfit best found on a Dark Magician girl.
But the wizard did not do anything, just blinked at the fact he had fallen victim to a prank.
Though it was not the end.
*Bang*
*Zip*
*Twang*
One after another trap was setoff.
After the second had gone off Sirius had gone on high alert and was suspicous of everything and yet still fell victim to another two pranks.
When Cassius finally saw the man, he had clearly fallen for almost every single trap he'd set since standing before him now was not the scrawny and haggard fourty year old skeleton of a man, but instead the living depiction of the D Magicician girl, sporting her pointy hat, and spiral staff, complete with heel.
A dopey smile even plastered on his/her face though the eyes were clearly doing anything but smiling.
"Hahahahahahahhaa"
Seeing the outcome, Cassius fell over laughing at the poor sight Sirius made after having fallen victim to the newest maurader.
Transfigurations, Polyjuice, Liplocker (Modified)...
The list went on but seeing the young lad on the floor unable to contain himself, Sirius looked to the wall catching sight of himself in the mirror and the anger faded replaced by amusement.
His fights with Snape in school was a one-sided prank war by the maurauders with Snape defending himself only with the use of spells no other had known.
But that amusement quickly turned serious.
Even as he wiped a tear from his eye Cassius caught the twinkle that returned to Sirius's eye.
And that gaze clearly said one thing and one thing only.
'IT is so on little Snape!'
~
The week that followed saw the return of one of the world most formidable pranksters, and the rise of a brand new world champion.
Sirius tried to fight back with all his might but try as hard as he could to get back at Cassius his attempts were... well lame.
And if he managed to suceed in any prank, Cassius retaliated easily three time worse.
During this week Cassius also slowly diseminated more and more information about his life, and things that have changed in the last ten years.
Such as his training under an Austrian wizard, before returning to Britain to attend school, his joining of the Arcanum a research institute broadening magical horizons.
Then his investigations into Lily Potter and his findings that after a simple car crash James had passed, but Lily retreated to the magical world to serve Dumbledore and hogwarts in safety while Harry was sent to live a cursed life with his aunt and uncle.
Lastly his previous year at hogwarts.
Where Sirius was stunned into silence once more to find Cassius was the heir to the true founders house, not only that but had himself his very own Hogwarts house with a formidable harem so to speak.
This remark of course caused Cassius's eyes to roll, i mean its not like it was something he hadnt though about but cmon all of them were still kids, not even properly in puberty or anything, even if he discounted the fact he was twenty years older in his mind, this wasnt something someone his age would be thinking about.
~
As the prank war betweent he two was heating up, Cassius laid his cards on the table.
"So... old man, are you ready to get revenge on some other people now?"
Cassius's provocation, caused Sirius to raise an eyebrow, or rather he would if he still had eyebrows, or even hair at all for that matter.
"Just who do you have in mind?"