I found an altar near the temple - answered a question and it said, "something happened". Is this significant?

I don't think so... since I don't recall that. What was the question?

This is in act 3 in the temple complex?

More like a riddle, really. Something about mother and father, one being clouds - whatever it was, I felt the answer had something to do with water/rain. One possible answer was "spit on the alder"; I think the one I picked was "wipe the alter clean". I did find another nearby that said it was the son of the other and asked another question/riddle. I have no recollection at all on that one but the correct answer appears to get the response, "something happened" with both. Incorrect kicks you out but you can try again. Once you get the "something happened", nothing else can be done. I didn't see anything in the strategy guide on it nor in a walk-through I found.

It is located south of the temple, south of a ridge that divides this area from the temple. I think there's a black imp cave nearby.

EDIT: OK, there's a talking crystal and making all four alters say, "something happened" yields a permanent something or other, speed I think.

Ok, I remember that now, in the crystal forest. I though you meant near the church in the temple complex.
If you search in the strategy guide for 'spitting' that should find it... or in the bookmarks, under Act 3, The Crsystal Forest, select Spirit of the Forest.