Okay, now I'm gonna go over his weapons. First is the Demon-Slayer Sword.
The DS Sword was Asta's first sword, and the one he usually ends up using because he keeps dropping the second one. Nonetheless, he can still use this thing like a pro. As stated, it's big, heavy, and blunt, making it perfect for smashing and stabbing. It can cut opponents if he slashes with the tip. It's a bone-breaker; a spine-crusher; you get the picture. It's massive.
It also doubles as a weapon that can cancel out magic.
The DS Sword may be blunt, but it cuts through magic stuff like hot butter. Asta typically goes in for one huge strike, cutting through anything in his way. When breaching compounds that have a magic barrier over them, Asta's always the go-to. When moving to an isolated underwater village, Asta's squad was stopped by a magic dome that encompassed the entire city. With the DS Sword alone, Asta cut through the wall and let his squad get in. He's even turned the sword to its flat and used it like a massive shield. Not just that, but an effective shield. He's used it like a baseball bat to deflect a magic fireball. It can even remove enchantments placed on people by tapping an infected individual's body with the cross guard.
Onto the Demon-Dweller (DW) Sword. This one can do practically everything the first one can, but it's lighter, faster, and skinnier.
Unlike the first sword, this one emphasizes the "anti-magic" aspect, which further convinced Asta to use it as a primary weapon over the DS Sword. As a passive trait, it will absorb magic in surrounding areas, continuously sapping magic power from those around Asta. However, it appears that Asta can control who the sword passively drains energy from. How much magic the sword drains depends on how close Asta is to people around him. The closer the sword is, the more magic it will drain from an individual. If someone, friend or foe, would to hold, be impaled by, or otherwise be touching the DW Sword, the blade would rapidly drain that person's magic out of them in a quick, continuous, metaphorical stream.
Secondly, Asta's allies/close friends can lend him their magic. While he can't use it, the DW Sword can. The magic power, based on attribute, would be shown in the blade's appearance. The black markings light up with the color of whatever magic has been absorbed, and the sword itself is surrounded with an aura.
Perhaps one of Asta's best accomplishments using his swords was keeping up with three fellow Magic Knights who stood against him for defending his friend; a noble who was having a hard time controlling her magic.
I might need to elaborate on that; people in Black Clover are socially classified as Commoners and Nobles. The difference is how they live, and how much magic they have. If one wishes, they could enroll in the Magic Knights; a group of warriors who defend the Clover Kingdom. The Magic Knights are divided into squads; Asta is a part of the Black Bulls, a known group of misfits.
Anyways, he was defending his friend; a noble who was a part of his squad. To her family, this was unthinkable, and they treated her as such. Asta retaliated against her family, nobles of a higher squad called the Silver Eagles, joined by a member of the top squad, the Golden Dawn. While defending his friend, the Magic Knights retaliated with magic, forcing Asta to draw his sword and fight back. He--
You know what? Just see for yourself.