Kinak
First Post
A wide variety of reasons, the most common of which is a sort of social contract. I've GMed for several groups where we had a spoken agreement of "I won't kill your character unless they've done something stupid enough to deserve it, just make their lives interesting." It occurs in widely varying degrees of formality, but most GMs will explain their GMing style at some point and that forms the basis for these shared expectations.Why do GMs feel the need to adjust the difficulty of an encounter mid stream like this?
And, sometimes, you just screwed up during prep. It's not pretty, but it definitely happens, especially when you homebrew. If the PCs go into what was supposed to be a minor encounter and it turns into a slaughterhouse because they made a tactical mistake, awesome. If it's because the dice went against them, that's less fine but I'll probably leave it lie. If it's because I screwed up when I was designing the monster they're fighting, I'll probably fix the design on the fly.
That said, I'm kind of glad mid-to-high-level D&D have raise dead effects to fall back on. It just takes too long for my players to build and, more importantly, learn a new high-level character. I'd be seriously tempted to lean on the d20 to avoid that, even ignoring the story issues.
It depends what you want in other areas. If you want combats to be tense and gain their tension from the threat of death, you might need to use some GM force. But if you're willing to reserve combats for major occasions or make victory mean something other than survival, then it doesn't require any recognizable force.If you want a lower body count do you need to use GM force?
There's a whole network of factors there.What effect does this have on player behavior and decision making?
As an example, a friend of mine is running a Pathfinder game for a party of casters. Throughout the game, there haven't been many combats, but they haven't been seriously challenged since low-level. But they won't engage unless forced, even when it's spelled out point-blank that they're at no risk in a given encounter.
As an example at the other end, my current group for Rise of the Runelords has suffered three PC deaths already and will probably have more before they're through. They usually try to talk instead of fight, but will cheerfully kill anyone who stands between them and the next chunk of the plot.
I'm sure GM force and the risk of PC death filters into both group's decisions, but it's buried under so many other factors it's completely indistinguishable.
Cheers!
Kinak