The PCs are 6th level. A single troll is CR 5, so it'd normally be a light encounter for the group. A winter wolf is normally CR 5 as well, but I reduced the stats a bit on this particular beast and called it a puppy. Together I figured they were EL 6, which is still a light encounter for the group because there are five PCs. (The ratings are normed for parties of four.)

Knowing the monsters was part of how everybody collaborated. The hunter knew about the troll's strengths— and vulnerabilities— because he's studied the requisite knowledge skill. The wizard figured out the smaller-than-normal winter wolf from a different knowledge skill she studied. "Great, we killed a puppy," she scoffed.