Trapper DC is defined by 2 elements: Max DC and Actual DC.Max DC is determined by trapper lvls+15.SD lvl = 2 trapper lvls.Rogue/ranger/assassin = 1 trapper lvl.All the rest = .5 trapper lvl. This is rounded down: 9 fighter lvls would be 4 trapper lvls. Actual DC is determined by (set trap skill+1d20 roll)/3 +15.So for example a character with 80 set trap skill and a max roll would have actual DC of: 100/3 = 33. +15 = 48. The highest actual DC the game engine allows for is 64 because skill points are capped at 127. That however doesn't count the roll, so highest set trap roll is 147.147/3 = 49. 49+15 = 64.