I'm running a campaign for a group of 6 level 8 characters. Last session, they went shopping, and I let them buy about 2 magic items each. On top of this, I let them each start with an extra feat and a free magic item when the campaign started (at level 8).
(Selling magic items to my players was a lot of fun for all of us! My question is not about whether that was a good idea – I believe it was the right call.)
Given how many nice things my players have, I'm thinking about balancing my encounters as though they were for a party of level 9 characters instead of level 8. Is this a reasonable approach for me to take?
Best Answer
In part it depends on the magic items. Did you give them magic items that were useful in combat? Like, have they mostly got +3 plate armor or have they mostly got sovereign glue?
Broadly, the answer to your question is yes: it's probably appropriate to give them more difficult encounters because they have nice stuff. But, especially at higher levels, the encounter tables are a very loose guideline anyway. You'll have to get a feel for what your group can handle.
Here is what I do when I'm uncertain: I start with an encounter that I'm expecting to be fairly easy, and then if the players seem to be winning too hard, I tell them reinforcements are showing up and I add more monsters of the same type.
The good news is that most players don't really want or need you to give them a super-difficult-but-still-survivable battle. If you give them a battle where everyone gets attacked once, and everyone gets to show off their cool abilities or items at least once, generally they'll be happy.
(source: I run a lot of games and this is what I do)