Tarvek is playing at what he always plays at--namely, anything that provides an advantage to himself. He no doubt believes that keeping the fact Klaus has been wasped secret will be to his advantage in the long run, or at least won't hurt anyone else.

In point of fact, he may be right. How would knowing Klaus has been wasped help them? All it would tell them is that somebody else possibly wants something in the town, and that's why it hasn't been destroyed. It still doesn't help them narrow down *what* they want.