Ron Weasley had deep scars on his arms from being attacked by brains with tentacles at the Department of Mysteries. Madam Pomfrey applied Dr. Ubbly's Oblivious Unction which did a little good, but she also observed that "thoughts could leave deeper scarring than almost anything else" (OP38).
It was Draco that attacked Harry first, and he was in the middle of casting a Cruciatus curse on Harry when Harry used Sectumsempra. Anyway, Snape healed Draco and there was no scars left. Dark magic is permanent unless the creator of a curse (dark magic) reverses it.
Ron Weasley got struck by a curse before this that made him act rather drunken and stupid, and made his brain fuzzy, so he foolishly summoned a brain out of the tank. The brain burst from the liquid, and as it spun toward Ron, what looked like ribbons of moving images flew from it, "unravelling like rolls of film".
AlastorAlastor "Mad-Eye" Moody (d. 27 July, 1997) was a pure-blood wizard, considered to be the most famous Auror of all time. He was a pivotal member of the Order of the Phoenix during the First and Second Wizarding Wars.
True Harry Potter fans know the books hold a special magic about them that the movies will just never capture. According to Pottermore, in the Harry Potter world, swears aren't meant to offend so much as they are to add emphasis—though Mrs. Weasley might argue otherwise.
Git - Mildly derogatory, meaning a foolish or contemptible person.
Mad-EyeMagical Eye: Moody's most notable possession was his magical eye, which was electric blue and earned him his nickname "Mad-Eye". This eye allows him to see through anything, such as wood, invisibility cloaks (including Harry Potter's invisibility cloak which was one of the Deathly Hallows) and the back of his head.
There's no penalty for keeping the key, except that you can't continue the guild questline. You don't get kicked out - rather, like most missions in Skyrim, you have virtually unlimited time to complete a quest.
The skeleton key is an unbreakable key that you have to return in order to continue with the Thieves questline. However, you can keep the skeleton key until you get the unbreakable pick perk, then continue the Thieves questline.