You cannot cast Fireball as a bonus action. Fireball is a spell that has a casting time of 1 action, which means it requires your full action to cast. Bonus actions, on the other hand, are a specific type of action that you can take on your turn in addition to your regular action.
In the rules of Dungeons and Dragons, the casting time of a spell is determined by the spell itself and is not affected by any other factors, such as the type of action you take or any abilities or features you may have. Fireball, being a 3rd-level spell, requires you to spend your action to cast it.
It’s worth noting that there are some spells, like Shillelagh and Magic Stone, that have a casting time of 1 bonus action. These spells are specifically designed to be cast as a bonus action, allowing you to use them in conjunction with your regular action or other bonus actions on your turn. However, Fireball is not one of these spells.
When it comes to casting multiple spells on your turn, the rules state that if you cast a spell as a bonus action, the only other spell you can cast during that turn is a cantrip with a casting time of 1 action. So, even if you were able to cast a spell as a bonus action, Fireball would not be eligible because it is not a cantrip and it requires an action to cast.
It’s important to follow the rules as written to maintain balance and fairness in the game. While it may be tempting to try and cast powerful spells like Fireball as bonus actions, the rules are in place to ensure that spells are balanced and have appropriate casting times.
In my personal experience as a player and dungeon master, I have seen situations where players have tried to bend the rules or find loopholes to cast spells more quickly or efficiently. However, it’s important to remember that the rules are there for a reason and altering them can have unintended consequences. It’s always best to consult the rulebooks and clarify any questions with your dungeon master to ensure a fair and enjoyable gaming experience for everyone involved.