We ran into this roadblock as well and went searching for an answer, there is a post on BGG that explains it.
In Short, HE HAS DAMAGE TOKENS ON HIM. Each token you add, reduces his health. We cross referenced this with other cards, and this is the only card that specifies the tokens placed on the cards as DAMAGE tokens.
I don't know what thread you were reading on BGG (didn't find it with a search), but I'm pretty sure that is incorrect. As I pointed out earlier in this thread, he has two numbers on him: the defense score in the lower right, and the attack score in the upper left. The attack score is a question mark so it is the only variable number. The defense score is always 25. As others have stated, he's a timer; you're not meant to kill him because if you could, you might as well take out the objective.
Would you mind please linking to the article you read on BGG? I'd really appreciate that.