Reminder: going up stairs is difficult terrain
Rules from AoN on Stairs, for reference.
>Stairs are difficult terrain for characters moving up them, and shoddy stairs might also be uneven ground. Some temples and giant-built structures have enormous stairs that are greater difficult terrain both up and down, or might require Climbing every step.
I'm running an urban adventure in Magnimar and realized just now that I totally forgot this rule. Gotta remember this next time to enhance the tactical aspect of combat!