With its loyalty secured, the only thing left to do now was to give the snake a name... There were still a few problems with this however...
"Erm... So, do you have a name I can call you?" Harry asks after the snake finally agrees to become his familiar.
It shakes its head, slowly slithering towards him and curling up next to his legs, "No... Namesss are uselesss for usss." it states.
...
Harry scratches his head with his healthy hand, "Okay... What gender are you? Unless you don't have one?... How do snakes even breed anyway." he mutters the last part to himself, getting a wry smile from Kali and a snort from the snake.
"I am male." it seethes, taking a hit to its pride after being misgendered by the boy.
Harry nods, thinking on what name would suit the snake... It's bony so, Boony? Ribsss... Skeletor...?
...
He sends a pleading look towards Kali for assistance, knowing that none of the names he could think of would be accepted by the prideful creature.
"How about, Nanthisk? It's the name of one of Exteneros' most legendary creatures. Before it was thrown into the abyss, it was said to be able to swallow whole islands." Kali says after thinking for a moment.
...
"You wisssh to curse me with the name of the dead!?" the snake asks, seeming offended by the name. Harry translates this to Kali, who isn't able to speak Parseltongue.
Kali gives it a glare, "No, but names have power. Naming you after a creature of such power may lend you some of it strength." she says, causing the snake to perk up as Harry translates.
"Isss that ssssoo?... Fine. Nanthisssk." it mutters, as if tasting the name as it says it.
Harry smiles, "Nanthisk it is then. I think it sounds pretty cool, thanks Kali."
She nods, "Thank me later, for now you need to complete the ritual." she says, prompting Harry to nod and move over to the ritual circle.
He goes through what they'd discussed prior, doing the requisite chant, cutting his palm and allowing Nanthisk to lick it with its forked tongue. And then, naming the snake. "I name thee, Nanthisk!" he loudly chants, causing the ritual circle to glow brightly before fading away as if it'd never existed in the first place... Fortunately, it also take away the ash that'd arrived with Nanthisk, preventing the inevitable clean up.
As this all happens, Nanthisk undergoes many small changes. First, his magic increases by around fifty percent, making his Calcifying Gaze far more powerful. If he used it on Harry now, half of his body would turn to bone in the same time period instead of just his arm.
Additionally, its steel-grey eyes slowly begin to turn green, mimicking Harry's eyes. Its girth also increases by a couple of centimetres, but the biggest change wasn't yet observable... The biggest thing the ritual provided to its contracted creatures was a large boost to their potential. Indeed, this also meant that the younger the familiar, the more powerful they'd generally become.
Obviously though, such a ritual was actually incredibly hard to learn. Most people who knew it either belonged to incredibly powerful Warlock families, or were strong demons like Kali who use them as a potential resource to trade. Luckily, Harry had been taught how to do it for free, giving him an opportunity that most Magicals, in and outside of earth, would kill for.
Once the changes Nanthisk was undergoing stopped, Harry found himself feeling a bit faint, his magic having been drained by the ritual to enhance and link itself to his familiar.
"Isss is complete?" Nanthisk asks with its now bright green eyes slowly blinking at him.
Kali nods, "Must be, otherwise I'd not be able to understand you..." she grins with her fangs showing, "Welcome to the family, Nanthisk... Wait here while I put Harry to sleep, you and I have some things to... Discuss." she states, somehow causes the snake's blood to go even colder.
With that, she sweeps Harry up into a hug and carries him out of the ritual room, through their treehouse and deposits him into his bed... While she might climb in beside him at this point, she had other matters of more importance to deal with.
First on the list, of course, was punishing Nanthisk for harming Harry in the first place... She was actually looking forward to brushing up on her torture techniques and wanted to experiment on which techniques were effective against snakes like Nanthisk.
While Harry was passed out in his bed, he was completely unaware of the goings-on in the treehouse... The maniacally laughing Kali chasing the incredibly scared Nanthisk as she swings a searingly hot brand like a madwoman.
The snake's yelps and begs for help and forgiveness were loud enough for the tribe living below the tree to hear, all of them wondering if Kali had finally lost it and turned on Harry.
When all was said and done, Nanthisk ended up having some of his bone plating torn from his body and turned into plates and other tools. The bone actually made quite powerful ingredients for certain potions, so the snake would end up having to 'contribute' to her creations whenever it caught her ire. While it might try to complain to Harry about its treatment, Kali was almost untouchable in the boy's mind, the most important person without a doubt who could do no wrong...
This was the first lesson Nanthisk learned... That power always came with a cost.