chaos scroll: a long time ago there was an event called "perfect pitch" which i wont explain anything about other than the fact you could have gotten chaos scrolls out of it. hackers found a bug and duped the hell out of it.
pink scroll (AKA WP ATT for 2h weapon 50%): a not so long time ago there was a different event, which i think even until today im not allowed to say how people (not hackers, anyone, including me, i got 7) got the pink scrolls. people found an exploit, a glitch, and abused it.
without any exploits, chaos scrolls drop VERY RARELY from zombie mushrooms, drum bunnies, cold eyes and other monsters, and pink scrolls are impossible to get from anyone other than a player. no monster drops it.
Chaos scroll dropped right when potential scrolls came out, it has nothing to do with halloween event... When potential scrolls came out chaos scrolls weren't as usefull, they were used to scroll PACs but now people want higher level capes for better potential stats, I THINK lol