Hodge Starkweather. A lovely name. Hodge just rolls off the tongue. And Starkweather calls to mind images of blossoming rose fields and golden sunsets. Oh, who are we kidding. It's a miserable-sounding name. And a perfect fit for the miserable jerk who wears it.
Hodge has two roles to play in City of Bones.
(1) He's a tutor to Jace and the other young Shadowhunters at the Institute, à la Professor X.
(2) He betrays them all! (Cue maniacal laughter.)
Let's talk about number one first.
Hodge seems to be a really good tutor. He has a huge library (always a plus), he's committed to green living by growing his own plants and medicines in the Institute's greenhouse, and he pretty much holds a whole Wikipedia's worth of knowledge about Shadowhunters and Idris and anything else magical inside his gray-haired, scarred head. He's the Giles to Jace's Buffy. He probably even taught them all to fight at some point, although we never see them training during the book.
So why did Hodge become a teacher? If you said the love of education and a commitment to bettering the lives of today's youth, you are absolutely… wrong. Hodge was a member of the Circle, Valentine's group dedicated to wiping out all Downworlders because they risked tainting the pure Shadowhunter bloodline. After their mission failed, the Clave punished those who survived. Hodge was one of them, and they condemned him to the Institute.
Their reasoning? According to Luke, "[Hodge] was devoting himself to his studies, they said, and would make a fine tutor for their children" (21.46). So that's why we had so much trouble getting babysitting jobs. We thought it was that line in his resume that read, "Participated in failed attempt at mass genocide."
On to number two. Hodge's betrayal is pretty cowardly. Instead of remaining loyal to the children who trusted him, he gives the Mortal Cup to Valentine.
"I am Valentine's man, it is true" (19.156), he says to Clary, which makes him sound like he should be a servant on Downton Abbey. Also, he couldn't even attack Clary himself. He had to have his little attack raven, Hugo, do it. Only when cornered in the alley does he use his own weapon, a bladed chakram, to attack Clary, the dangerous fifteen-year-old mortal girl with no dangerous powers to speak of. Trés manly, Hodge.
To his credit, it does sound like it was an agonizing decision. He lived his life almost as a vampire, not being able to go outside and breathe fresh air. He also makes Valentine promise not to hurt Jace. Even so, we wouldn't have been disappointed if Luke did bite his head off in Rats' Alley.