. ▁C ere ber us ▁is ▁the ▁son ▁of ▁E ch id na ▁and ▁Ty phon . ▁ ▁Ch ary b dis ▁– ▁One ▁of ▁the ▁two ▁mon sters ▁( the ▁other ▁being ▁S cy lla ) ▁who ▁live ▁on ▁either ▁side ▁of ▁a ▁narrow ▁channel ▁of ▁water ▁( the ▁entrance ▁to ▁the ▁Sea ▁of ▁Mon sters ). ▁She ▁takes ▁the ▁form ▁of ▁a ▁giant ▁mouth ▁that ▁sw all ows ▁and ▁releases ▁water , ▁creating ▁wh irl po ols . ▁she ▁is ▁described ▁by ▁Per cy ▁as ▁an ▁" orth od ont ist ' s ▁night m are ". ▁ ▁Ch im era ▁– ▁A ▁three - head ed ▁be ast ▁that ▁is ▁part ▁l ion , ▁part ▁go at , ▁and ▁has ▁a ▁s nake - head ed ▁tail . ▁It ▁is ▁first ▁seen ▁in ▁the ▁form ▁of ▁a ▁Ch ih u ah ua . ▁It ▁confront ed ▁Per cy ▁at op ▁the ▁St . ▁Louis ▁Arch ▁alongside ▁its ▁mother , ▁E ch id na . ▁Over wh el med ▁by ▁the ▁creature ▁and ▁poison ed ▁by ▁its ▁s nake ▁head , ▁Per cy ▁was ▁forced ▁to ▁jump ▁into ▁the ▁water ▁far ▁below ▁to ▁escape ▁it . ▁It ▁disappeared ▁after ▁Per cy ▁dove ▁into ▁the ▁water . ▁ ▁Cla z mon ian ▁S ow ▁– ▁A ▁flying ▁p ig ▁that ▁appeared ▁directly ▁after ▁Hyper ion ▁was ▁defeated . ▁Per cy ▁defe ats ▁it ▁with ▁the ▁help ▁of ▁Black jack , ▁a ▁statue ▁of ▁Herm es , ▁and ▁the ▁New ▁York ▁Public ▁Library