Answer:
Describes universities like Harvard and can be poisonous.
What lies in a tunnel of darkness. That can only attack when pulled back?
Stealthy as a shadow in the dead of night, cunning but affectionate if given a bite. Never owned but often loved. At my sport considered cruel, but that's because you never know me at all.
Thirty white horses on a red hill, First they champ, Then they stamp, Then they stand still.
Kills the bad ones and the sad ones. Tightens to fit, so one size fits.
I am your mother's brother's only brother in law. Who am I?