Morgot's servants more terrifying than Sauron's?

[William Cloud Hicklin]

Originally Posted by Inziladun

What I've wondered is this: Glauring, when he applies his power, can compel even the strong-willed, like Túrin and Nienor, to obey his commands. Yet Morgoth was unable to force the location of Gondolin out of Húrin. Maybe he should have let Glaurung have a go?

Not exactly. Glaurung could paralyze Turin, and cozen him, but there's no indication that he could force him actively to do or say anything. Instead Glaurung relied on deceit (and a diabolical knowledge of his victim's psyche). Nienor he simply mind-wiped. Both are very different from forcing them to answer questions. Similarly Morgoth could poison Hurin's mind to the point that he did the Dark Lord's will unwittingly, but he certainly wasn't controlling him.