▁that ▁there ▁were ▁two ▁cam ps , ▁one ▁Greek ▁and ▁one ▁Roman , ▁before ▁The ▁Lost ▁Hero , ▁making ▁him ▁an ▁important ▁l ia ison ▁between ▁the ▁two ▁groups ▁in ▁the ▁latter ▁series . ▁He ▁brings ▁his ▁half ▁sister ▁Haz el ▁back ▁from ▁the ▁dead ▁and ▁establish es ▁her ▁at ▁Camp ▁Jup iter . ▁At ▁the ▁end ▁of ▁The ▁Son ▁of ▁Ne pt une , ▁N ico ▁travel s ▁through ▁T art arus ▁to ▁find ▁the ▁mon str ous ▁side ▁of ▁the ▁Do ors ▁of ▁Death , ▁an ▁experience ▁which ▁leaves ▁him ▁ha unted ▁and ▁weak . ▁In ▁The ▁Blood ▁of ▁Olymp us , ▁he ▁nearly ▁dies ▁several ▁times ▁while ▁" shadow - tra vel ing ", ▁which ▁involves ▁mel ting ▁into ▁sh adows ▁and ▁tele port ing ▁himself ▁to ▁different ▁places . ▁His ▁sister ▁whom ▁he ▁brought ▁back ▁from ▁the ▁dead , ▁who ▁goes ▁by ▁the ▁name ▁Haz el ▁Le ves que , ▁is ▁the ▁daughter ▁of ▁H ades ' ▁Roman ▁identity ▁Pl uto . ▁He ▁is ▁a ▁very ▁mo ody ▁character ▁ ▁Rach el ▁Elizabeth ▁D are ▁Rach el ▁is ▁a ▁mort al ▁girl ▁who ▁can ▁see ▁through ▁the ▁M ist , ▁the ▁force ▁that ▁obsc ures ▁gods ▁and ▁mon sters ▁from ▁most ▁mort als . ▁Her ▁father , ▁Will ▁D are , ▁is ▁a ▁rich ▁business man , ▁a ▁fact ▁which ▁she ▁is ▁rather ▁ad verse ▁to . ▁She ▁first ▁meets ▁Per cy ▁in ▁The ▁T itan ' s ▁Cur se ▁at ▁the ▁Ho over ▁Dam . ▁In ▁The ▁Battle