▁later ▁cast ▁as ▁a ▁character ▁named ▁Miss y , ▁described ▁as ▁" The ▁Gate keeper ▁of ▁the ▁N eth ers phere " ▁and ▁was ▁originally ▁announced ▁to ▁be ▁featured ▁in ▁the ▁series ▁finale , ▁however , ▁G ome z ▁also ▁appeared ▁in ▁the ▁series ' ▁first , ▁second , ▁sixth , ▁nin th ▁and ▁t enth ▁episodes ▁as ▁part ▁of ▁a ▁rec urr ing ▁story ▁arc . ▁In ▁" D ark ▁Water ", ▁it ▁was ▁revealed ▁that ▁Miss y ▁is ▁in ▁fact ▁The ▁Master , ▁with ▁G ome z ▁taking ▁over ▁the ▁role ▁from ▁John ▁Sim m . ▁ ▁Production ▁ ▁Development ▁At ▁Com ic - Con ▁ 2 0 1 3 , ▁Steven ▁M off at ▁said ▁that , ▁although ▁much ▁of ▁the ▁focus ▁at ▁that ▁point ▁remained ▁on ▁the ▁ 5 0 th ▁anni versary ▁and ▁Christmas ▁spe ci als , ▁development ▁for ▁series ▁ 8 ▁was ▁under ▁way : ▁ ▁In ▁an ▁interview ▁with ▁Doctor ▁Who ▁Magazine , ▁M off at ▁li ken ed ▁his ▁initial ▁plans ▁for ▁the ▁Tw elf th ▁Doctor ▁to ▁Tom ▁Baker ' s ▁first ▁season , ▁with ▁the ▁Doctor ▁being ▁tricky ▁to ▁deal ▁with ▁at ▁the ▁beginning , ▁but ▁with ▁the ▁benefit ▁of ▁familiar ▁characters ▁to ▁ease ▁through ▁the ▁transition ; ▁M off at ▁also ▁commented ▁on ▁the ▁situation ▁of ▁Clara ▁having ▁to ▁deal ▁with ▁the ▁Doctor ▁changing . ▁M off at ▁has ▁also ▁stated ▁that , ▁unlike ▁the ▁situation ▁with ▁Col in ▁Baker , ▁reference ▁will ▁be ▁made ▁to ▁Peter ▁Cap ald i '