Gravie Derment was an eight Level Wizard and a head of the Sages of the Unknown Shadow at Unseen University.
During the events of Sourcery, he met with Spelter and the five remaining order heads to decide how to deal with Archchancellor Coin. He very succinctly explains why it was important to stand up to Coin in the following scene.
"(Gravie) thumped his fist on the table.
'Good grief, man!' he snapped. 'Some child wanders in out of the night, beats two of the University's finest, sits down in the Archchancellor's chair and you wonder if we have a problem? The boy's a natural! From what we've seen tonight, there isn't a wizard on the Disc who could stand against him!'
'Why should we stand against him?' said Spelter, in a reasonable tone of voice.
'Because he's more powerful than we are!'
Gravie realizes, unlike the other wizards that if you let someone else get the better of you, in a world of "dead man's shoes: you are as good as dead. Spelter, in contrast seems to belong to the school of wizarding that says "don't worry about anything as long as you are getting your three square meals a day.