You decide that if an when the players make it a priority with their choices.
Addendum to the "Are you sure you want to do that" bullet: if a player ever does something that seems nonsensical to you, ask them what they expect to achieve by doing that. Understanding their motivation is often what resolves the miscommunication and/or allows you to steer them towards a better way to do what they're trying to do.
I read once that the earliest edition(s?) didn't have Rogue as a separate class, that everyone would be searching for traps and such. And when Rogue was added with the explicit ability to detect traps, it caused a crises because suddenly that implied that no one else had that ability.
It's the cats you gotta worry about.
There are a couple ways to get auto-generated transcripts from youtube (eg https://www.howtogeek.com/793947/how-to-get-the-transcript-of-a-youtube-video/ ), but there are enough errors and bad UI that I find reading them to be more miserable than just watching the video.
Main quest? Weird tangent? They're the same picture!
God you just described my prep in a nutshell. This is how they ended up fighting an orchestra
Hi. I'm sorry, this looks like a legitimately great book, but we only allow self promotion from active users. I am removing your post, but if you are interested in becoming a member of our community, you would be welcome to post 1 self-promo per week in the future.
Ok. It was just an example of a way you might make an encounter revolve around a spell, not an exhaustively researched adventure module.
There are ways. You could, for example, set up a bbeg where that's his whole deal. The townsfolk are scared of this guy because he has the supernatural power to just kill you, straight-up. Maybe the questline leading up to their encounter involves the players finding defenses or counters or sabotaging his supply of spell components or whatever, such that, if they DO get power-word-killed, it's because they had ample opportunities to not, and failed to take them.
Sometimes that can be fun, but only if everyone at the table is onboard for a wild tangent. If the other players are bored as shit while the special snowflake starts a unicorn breeding operation, it's time to use that No. And you, the DM, are included in that too; if your players want to drag you off to write every book in the library and that's not fun for you, you have the right to say "hey maybe you should play the game I made for you instead."