Just because I wanted to, I added this Italian part first. Skip the bold to the English below it.

Nico DiAngelo is a perfect example of character development. I don't think Rick ever intended for Bianca to live. Her death was beneficial to Nico's character development.

First, you might be asking: What the Hades is character development and why should I care?

Character development is how your characters grow, or develop. Bianca dying contributed to Nico's character development.

Remember Nico asking Percy all of those questions about Riptide, and thinking everything was so cool?

Now he keeps himself guarded, has more walls than an office complex, and is dark and moody.

Why? Because his character developed. Your main character should not be exactly the same at the beginning and the end.

Let's pretend I have a character named Otera, nicknamed Tera, nicknamed Terror. She's a daughter of Ares, and she's going on a quest. She's good with the spear, and is strong.

She's a bully, but nice and kind to her friends. Now, we want her to develop, and grow. We don't want her acting the same at the beginning and at the end.

Character development takes time, so never rush it. Like, Clarisse is not the same at The Lightning Thief and at The Last Olympian. We see she cares about people, like Chris Rodriguez. We see her go from the bully, to the misunderstood.

She still has bully tendencies, but she is a real person to the readers. If she had stayed a bully, never wavering, reusing her old insults, do you think her character would stay as 3 dimensional and deep?

No way! That is good character development right there.

Now, back to Tera. She's going on a quest with Noah Jackson, the upstart son of Percy Jackson and Annabeth. She has to be the bully, just like her infamous half sister and aunt, Clarisse La Rue. Who knew Clarisse had a mortal sister?

She tries to keep up the facade that she's big and strong. Then one night, Noah hears her talking to her mom in an iris message. Her mom is screaming at her, and saying it's her fault that monsters are coming.

Tears are streaming down Tera's voice, as she tries to guide her mom out of this troublesome situation. Suddenly, the monster rips open the closet door. Her mother lets out a piercing scream as she is shadow traveled away by the hellhound.

Tera swipes her hand through the mist and cries. Noah comes from behind and puts an arm around her. Surprisingly, she doesn't push it off, and stays there, crying, while Noah comforts her.

You see how her character developed from big bad bully to misunderstood kid trying to make it through life? Anybody can use that Tera idea, just tell me because I would want to read that book.

Character DEvelopment is a big part of characters and how the readers percieve them. You better have it in your story or it's going to be a snooze.