Asking for a yes/no user input
characters should be named Character
Add some type hints
Use f-strings
Use int or float for power score, not str
Use a @property where appropriate
As-is, there isn't a lot of advantage to separating your prompt strings into variables
For the data method, don't force a print - just return a string and print at the outer level
Add a main
Square brackets around an input choice implies that it is the default to be selected on 'enter'
Simplify your yes/no check to only care about the first letter; anything more complicated isn't all that useful
Add an input validation loop

Suggested:
class Character:
    def __init__(
        self,
        title: str,
        name: str,
        power_score: int,
        biography: str = 'Not much is known about this character',
    ):
        self.title = title
        self.name = name
        self.power_score = power_score
        self.biography = biography

    @property
    def full_name(self) -&gt; str:
        return f'{self.title} {self.name}'

    @property
    def data(self) -&gt; str:
        return (
            f'{self.title} {self.name} | Power score - {self.power_score} -\n'
            f'{self.biography}'
        )


def ascii_art():
    # Y(Height) of ascii-art
    z = 12
    for x in range(z):
        hyphens = &quot;-&quot; * (z-x)
        print(hyphens + &quot;*&quot; * x + &quot; &quot; * x + hyphens)


def input_yesno(prompt: str) -&gt; bool:
    full_prompt = f'{prompt} ([Yes]/No): '
    while True:
        answer = input(full_prompt).strip()
        if answer == '':
            return True

        answer = answer[0].lower()
        if answer == 'y':
            return True
        if answer == 'n':
            return False
        print('ERROR')


def main():
    ascii_art()
    if not input_yesno('Are you ready to play'):
        return

    is_hero = input_yesno('Do you want to be a Hero')
    print('\nYou have selected', end=' ')
    if is_hero:
        print('to be a hero')
        character = Character('Barbarian', 'Cider', 4854)
    else:
        print('not to be a hero')
        character = Character('Lord', 'Cido', 7910)

    print(&quot;\nYour character's profile:&quot;)
    print(character.data)


if __name__ == '__main__':
    main()