All of us have grown up with stories and mythologies of our own religious beliefs. Gods, lesser-gods, monsters, demons, angels, etc. Start with your character, not a vague concept. Also, etc. sounds way too casual to belong in a pitch to an agent. Karan also thought that these were only stories. Until he discovered that his ancestry has direct relations to the Ramayan. I don't know what this word means. Is it one you've made up or a mythological word to a real-world culture? Again, I don't know and it feels like you're assuming the reader will. And you've yet to personify Karan or give us a reason to be interested in HIM, not his "destiny".
Karan meets Chhaya at a party and develops an instant liking to her. Okay, why? What makes her special? Contrary to his best friend Harshit’s this is the fourth name you've given us (counting Ramayan). That's probably too many; you could likely call Harshit "the best friend" or w/e and that would be fine. Assuming you even need to mention this character in the query advice, Karan decides to express his feelings to her. Unknown to them, it is revealed If it's unknown to them, how is it revealed? It sounds like there's a part of your book that happens behind Karan's back where it's revealed that Chhaya is an alien, but don't word it like that in a query. A query is almost like a little story in itself, and in a real story, you wouldn't just type "Oh and Chhaya's a martian." that Chhaya is an extra-terrestrial who has been looking for Karan.
Before Karan could tell Chhaya about his feelings, she reveals that she belongs to a class of extra-terrestrials believed by the ancient humans to be the agents of God. To Karan’s dismay, she says that he is part of one of the 8 lineages of Possessors, that have carried the genes with the 8 Siddhis of Hanuman since the period of the Ramayan Again, I don't know if these are words you have invented or if they are actual mythological references. Either way, you should assume the reader doesn't know, and either explain (which would take more of the precious, limited space you have in a query) or cut it down and include only the most necessary facts. She needs his help in assimilating the other 8 Possessors together to stop an impending civil war in the galaxy. Plot plot plot. Lots of books are about war and galaxies and stuff. You're not going to win an agent by telling them that your book is #24000000 that features a war. I know nothing about what kind of person Karan is. He likes a girl and has a destiny. How many books/movies/etc have main characters that you could describe as "They like a girl, and they have a destiny"?
As a shocked Karan narrates this to Harshit Not to be immature, but if you're aiming this at English speaking readers, the fact that one of your characters' name will read to most English speakers as "Harsh Shit" ... might be enough reason to change the name, he in turn reveals that he is part of a clan called the Protectors assigned to ensure the safety and succession of the genes through the Possessors. Another faction to keep track of? Waaaaaay too much stuff, and it's not being portrayed in an engaging manner. :/
Now, a heartbroken and hurt Karan must decide between forgiving those who deceived him and accept his destiny; or condemning them and cause the loss of billions of lives across the galaxy ...I'm assuming you didn't write a book where the main character sits at home and lives a normal life instead of going out and being a galactic hero. Therefore, there's no tension in this "choice". . But none of his choices, Why this comma? come without a cost.
Siddhi: Vasitva On the title, it has two words that I don't know. It's come up a lot, and if the words you're using are based on a real-world culture, it's one I'm not familiar with. My own shortcoming to be sure, but if you intend to sell this to a primarily English-speaking audience, I think you should assume anyone reading this will have no familiarity with these words. (Again, assuming they're from an existing culture)., is complete at 100000 words and is ready for your consideration.
So, I noticed two major issues immediately. First, you have not made your character, Karan, engaging at all. He doesn't do anything of consequence in the query, except have things revealed to him. That's very passive and I don't believe that sort of writing will get you an agent.
Second, there is too much minutia in here. Chayya is a this and that, and Harshit is a someone who does this, and Karan is an inheritor of this and that, which belonged to these people and that's apparently important for some reason. That may sound like a harsh summary of your query, but to the reader, that's what it will sounds like. Most of the words you use aren't going to have meaning for anyone; you need to choose the most important parts/characters (probably only need 1 or 2 named people or factions in the query), and then make a query based on that.
Start with Karan; give us a very quick and intriguing look at what kind of person he is. NOT HIS DESTINY. You could tell us he is the inheritor of some great galactic empire, or that he is a pauper living off scraps on the street. That doesn't let me envision who. He. Is. Is he a nice person? Teenage, adult? Is he impulsive, or considerate? Is he a fighter, or a runner? Give us one or two lines that grab our attention while letting us know who Karan actually is.
Then, and I know it can be hard, force yourself to only include two proper names in the query, and I mean names for people or factions or what have you. Right now, you have Karan, Ramayan, Chhaya, Harshit, Possessors, Sigghis, Hanuman, and Protectors. Waaaaay too many, and it doesn't help that the two factions who are apparently at odds (The Possessors and Protectors) have such similar names. Whether or not the query that actually gets you published features more than two names, I believe writing at least one version with only two can help you see how much you can trim this down.
Lastly, decide how much you actually need to put into the query. Usually, you don't have a lot of room to flesh out every story, character or subplot in your book into 200-ish words. It's up to you ultimately what parts of your story make it into the book, but you cannot fit the whole thing into a few paragraphs, and have it all sound interesting. Something, likely several things, will have to go.
Anywho, those are my thoughts. Obviously, it is up to you to decide what to do with your query, but I hope my ramblings will help! :)