▁with ▁the ▁car avan , ▁of ▁which ▁Burn ing ▁Tower ▁is ▁also ▁a ▁part , ▁to ▁discover ▁the ▁source ▁of ▁the ▁birds . ▁They ▁travel ▁to ▁the ▁southern ▁city ▁of ▁Cond ige o ▁and ▁then ▁to ▁C res cent ▁City , ▁defe ating ▁terror ▁bird ▁attacks ▁along ▁the ▁way . ▁In ▁C res cent ▁City , ▁they ▁are ▁joined ▁by ▁Reg ap isk , ▁who ▁has ▁escaped ▁from ▁his ▁ship . ▁The ▁three ▁of ▁them ▁travel ▁on ▁to ▁the ▁high - mag ic ▁city ▁of ▁A zt lan , ▁where ▁Reg ap isk ▁re de ems ▁himself . ▁ ▁The ▁authors ▁research ed ▁Az te c ▁culture ▁for ▁the ▁book , ▁and ▁many ▁aspects ▁of ▁the ▁culture ▁dep icted ▁in ▁the ▁book ▁are ▁based ▁on ▁that ▁research . ▁This ▁is ▁explained ▁in ▁a ▁brief ▁note ▁at ▁the ▁end ▁of ▁the ▁book . ▁Also ▁mentioned ▁is ▁that ▁within ▁the ▁described ▁tim eline , ▁the ▁terror ▁birds ▁continued ▁to ▁exist ▁until ▁long ▁after ▁humans ▁spread ▁through ▁the ▁Amer icas ; ▁this ▁is ▁based ▁on ▁the ▁North ▁American ▁ph or usr h ac id ▁T itan is ▁wall eri ▁( but ▁see ▁Mc F ad den ▁et ▁al . ▁ 2 0 0 7 ). ▁ ▁S ources ▁ ▁Mc F ad den , ▁Bruce ; ▁L abs - H och stein , ▁Jo ann ; ▁H ul bert , ▁Richard ▁C . ▁Jr . ▁& ▁B ask in , ▁Jon ▁A . ▁( 2 0 0 7 ): ▁Re vised ▁age ▁of ▁the ▁late ▁Ne