Seasonone(10episodes)oftheshowfeaturesonagingmasterSenseiWuashestrugglestotrainfouryoungNinjainthewaysofanancientbattleartcalledSpinjitzutodefeathisevilbrotherLordGarmadon,ruler[butnotking]oftheunderworld,andstophimfromgainingfourgoldenweaponswhichwouldmakehispowerlimitless.Thoughmanyskeletoncharactersareintroduced,onlyKrunchaandNuckalappearinseasontwo, makingcameosassubstituteteachers.Seasontwo(13episodes)focusesonGarmadon'syoungsonLloydGarmadon,who,lackingproperfathering,hasreleasedanancientevilarmyofsnakes,whoholduniquepowers.ThefourNinjamuststopthemfromunitingtounleashtheGreatDevourer,anevilwithpowertoconsumetheland.