All castles in Heroes 3.

A champion is simply not comparable to a death knight, no matter how you look at it. Just think about it – while the champion is searching for a target further away from itself to attack with a running start (and often it makes sense to attack nearby targets, not distant ones, because getting into the thick of it can have bad consequences for the aforementioned champions), the death knight will simply strike with double damage (the probability of which is very high). And in terms of health, the champion has nothing to boast about compared to the death knight.

Personally, I really like increasing luck when I have death knights in my army; you can understand why.