Was wondering if I could get an opinion on my first character's backstory. I'm a noob so this is all new to me. I'm playing a tiefling Blood Hunter (yeah CR whatever) and I'm just wondering if his backstory makes any sense. 

Born aboard the slave ship "Aimless Arrow" during a storm to a tiefling mother and unspecified father, given the infernal name "Echo" due to the slaves being held below deck and only able to hear the wind and thunder. The ship was captained by a human captain named Everett, and his tiefling lieutenant, who's pity and influence allowed Echo to be spared and kept with his mother. At age five, Echo released the slaver captain's pet songbird from its cage in his quarters out of sympathy. For this, the captain Everett ordered his mother sold, and the boy placed in a small cage in the pitch blackness of the ship for months. He was beaten daily and starved until skeletal and nicknamed "Sparrow" by the slavers. During this time his mind repressed the memory of his Infernal name. The tiefling lieutenant, who would not take part in the beatings then noticed Sparrow's resilience and ferocity towards his captors, particularly his indifference to threats of pain or physical harm. Because of this, Everett allowed Sparrow to be released, conditioned and trained to fight, at first solely by the tiefling lieutenant but then by more of the slavers who welcomed the chance to wail on the slave boy. While small, Sparrow's agility and ferocity marked him in combat, as well as his unflinching ability to withstand pain. He was deployed in skirmishes with rival slave ships. During one such clash, the tiefling lieutenant was gravely wounded by an enemy archer. Upon seeing this, Sparrow flew into a rage, casting aside his weapons and falling on the attacker with his bare hands. Sparrow beat the archer's face to a mess of blood, eventually tearing open his chest with his horns. Both terrified and impressed by this display, Everett then offered Sparrow the chance to replace his former lieutenant, on the condition that his horns were crudely sawed from his head as show of both loyalty and dis-ownership of his tiefling nature. Sparrow's horns are still assymetrical, jagged stumps a few inches long. He then served as both Everett's battle commander and slave driver, a role which he embraced with autonomous, unfeeling calm for many years. He was also free to move about the Aimless Arrow, during the day occupying a dark cabin below deck and at night perched in the crow's nest, his tiefling night eye making him ideal as a scout. Some time after turning twenty three (even though he himself is not entirely sure of his exact age) Sparrow helped to capture what was assumed to be a merchant vessel during an incredibly violent storm, which was then discovered to be occupied by tiefling refugees fleeing ethnic cleansing. Enraged, Everett ordered the ship sunk with all souls aboard. As the memory of his mother and the cage resurfaced, Sparrow turned on Everett. As the storm raged around the two, the crew rushed back to the Aimless Arrow. Bested in combat, Sparrow was thrown wounded into the ocean as the refugee ship was overturned. While Everett most likely escaped, Sparrow to this day is unsure as to whether or not Everett is still alive. Nevertheless Sparrow is driven by an instinctive will to hunt him. Washing ashore, Sparrow was found near death by a blood huntress of the Order of the Ghostslayer. Given the order's focus on the understanding of death and the final moments of living things, the blood huntress took the broken body to a nearby cave, intending to observe the moment Sparrow died and meditate upon it. When after three days Sparrow was still breathing, the blood huntress decided to nurse him back to health. During his recovery they discussed death, and his experiences of it. How understanding of life can only be understood by understanding the very last moment of it, and the space afterwards. Sparrow lamented that he would not truly understand life until he found his mother, nor death until he watched the death of Everett. After months in the cave, Sparrow took his first steps on dry land after twenty three years at sea. Sparrow was then inducted into the Order of the Ghostslayer. Told that the Hunter's Bane alchemical process would either give him the strength to hunt his enemies or kill him, he willingly submitted to the process. During further training the order honed his skills in combat, and also trained him in blood magic. Aware of his tolerance for pain, Sparrow pursued the knowledge surrounding the Blood Curse of Mutual Suffering, allowing him to willingly take physical punishment which is immediately reflected back on his attacker. Sparrow also adopted the Crimson Rite of Storms in memory of both the night he was born and Everett's escaped, allowing him to imbue his weapon with lightning power even while causing him physical harm. Pain is a necessary means to the end of defeating moral abhorrence. While Sparrow is loosely aligned with the Order, their focus on studying death in order to fight the undead is entirely secondary to him. During his training his will to find his mother was eventually dwarfed by his will to kill Everett, but after several years the trail has gone cold and Sparrow has settled for hunting slavers in general. He reserved his moments of swift but incredible violence for them in particular. At other times he is usually calm, preferring to avoid violence but not shying from it. He will happily pursue sellsword work slaying monsters and beasts for coin, but will pursue slavers and violent racists of his own accord.

Make sure to work with your DM too for what they are looking for. When I run games, I generally want things that I can tie into the plot or adventures like some of the following, which it seems like you have covered

• an ally from your past
• an enemy from your past
• any organizational ties
• what motivates you to adventure

As a personal preference, I would not want or need all of the grim details. Leaving it at "Sparrow was mistreated and tortured by the crew" is sufficient.

Yeah, it’s a common new player thing to really nail down the backstory, only to have it never come up (and all too often find DMs or other players getting slightly annoyed that you spent more than 15 seconds introducing your character.). I know I’ve certainly done it. One thing I’ve been told a few times is no one cares about your backstory except you. If you’ve got a really RP heavy homebrew game with a world class DM who has the time and inclination to study all the characters’ stories and work them into his plot, then awesome. We all envy you. But more likely you have a DM who barely had time after work to be able to pull together his maps and stat blocks for tonight’s game.

My advice based on what I’m still learning is build your character around a quirk (such as irrational hatred for pigeons) or a goal (such as I’m looking to get strong enough to Solo a Sone Giant, because reasons.) and those characters will shine in average games more than one that you filled all the holes in their backstory. Other players want to engage those characters, to feed their quirks and give them a chance to react. (“I cast minor illusion and say Hey! Bob, look over there! Pigeons within 100 ft of innocent children!”)

I have no idea I just wanna say it sounds cool 

Make sure that your character has a goal and tell the DM about it so they can work it into the campaign. The first character I had, I tried to make my own backstory and it didn't have any goal for the character so halfway through, I just reverted back to the pre generated backstory and it was a bit of a disaster. You can keep this long version for yourself, but on your character sheet, simplify it to the main points that affected who the character is today. It is amazing how much work you've put into this, just make sure that you have a goal, enemies and allies, and a motivation and that you tell the DM about all of it so the campaign doesn't go off the rails.

The quirk is a very good suggestion.  Playing a character that stands out will make everyone remember.  Talking differently, having an irrational fear, and uncompromising attitude, etc. all make for a vivid role play session.  As a DM, I always like to base my campaigns around character backstories, but at the same time those backstories had to fit within a scope that allows weaving of a backstories between all parties to make an epic tale of adventure between them.

you may want to check with the DM if it is okay because there may not be slavers in the world he has created