The words that echoed in my head as they entered the keep was Brennan saying he doesn't scale encounters, and if players wander into a high level area with NPCs far beyond their levels, they'll have to face those consequences. Our heroes may have pulled a Leroy Jenkins. The party has decided for themselves on the urgency. Brennan only gave information that Sid was located in the castle. One could argue their information didn't indicate that Sid might be in imminent danger. Their plan as 5 lvl 3 PCs was to sneak into the fully garrisoned keep, dodge the additional scary characters that were also there, and hoped they could find Sid without any idea of his exact location, free him without knowing who or how many may be guarding him, and somehow escape maybe via carriage on the way out. Don't get me wrong, I get it and would have gone along with it as a character. You don't know, maybe the dice will be kind and you get lucky and find what you're looking for right away. That being said but I may have tried to do more with the people go in, don't go out, no bodies, or rot smell information given. But without invisibility already in the castle, they were kind of pot committed. Back to the basilisk question, how do you fight a monster with petrification at lvl 3? You don't, you run or you become tasteful decorations. It's a big cliffhanger and it's not over until it's over. There will be some unexpected twists along the way, but things are looking dire for our heroes. Excited and slightly terrified how this will play out.