[Question] Team sensitive events

Do anyone know how to make events happen only when you have a certain pokemon in your team like the regis mission where you needed wailord and relicant?

The image attached show how to make a simple event that just checks if certain Pokemon are in the player's party. If you are looking to check to see if the Pokemon are located is a specific slot in the player's party then I would recommend checking out this Wiki page.
https://essentialsdocs.fandom.com/wiki/Editing_a_Pokémon

GT-Baka's attached script is the correct answer, however it doesn't check if Relicanth is in the party if the player doesn't have Wailord. This is what you could do: