>>96149279
Id let them get creative. Depending on the setting they might have magic or some gadget that does the trick. Finding a different way into the sewers is also possible. Maybe there's a character with above normal strength. Maybe they can jury-rig some items to use for leverage. It's also pretty hilarious to come to the manhole cover carrying all the stuff you prepared, and no one has the crowbar. Make it a funny roleplay moment.

Jesus, there are countless ways around this. Cant any of you improvise?

>final boss of the series is the protagonist from the first game