Adjusting the Final Boss
So the final encounter with the Black Spider as written is: Nezznar, four giant spiders, two bugbears. My party is four level 5 players using 2024 rules. So I adjusted it to: Nezznar is the CR6 Mage, one bugbear warrior (Nezznar's bodyguard), one hobgoblin captain (Nezznar's lieutenant), and four giant spiders.
Let me tell you, it was a good fight! The spiders locked the players down for a round or two right at the hallway leading to the temple before they killed all four. They killed the bugbear easily. The captain attacking with advantage downed a player before being killed. That left Nezznar the Mage.
He threw a fireball on the second round and idk how nobody went down. His arcane burst attacking three times per turn hit way harder than I expected. Counterspell and shield were invaluable. But after another few rounds, he wasn't even bloodied, still had a fireball and cone of cold, and was staring down battered 3 PCs. So he fell back to gather the 5 bugbears. One PC chased after him and went down for it. Eventually, Nezznar fled with two bugbears in tow and the party broke contact as well to end the session.
They're going to go back the way they came, where they'll run into the rejuvenated flame skull. I'm gonna let them short rest before getting there, and have Nezznar and his bugbears set up an ambush at the entrance to the cave. Again, he still has a fireball, a cone of cold, a counterspell, an invisibility, and a misty step, and is not bloodied. This could get very rough, but I do like how I adjusted this encounter for 2024 rules. Hopefully my party will learn not to stay so clustered up against a Mage boss. But this adventure is far from over.