▁fourth ▁edition ▁was ▁directly ▁compatible ▁with ▁ 2 nd ▁Edition ▁AD & D ▁with ▁some ▁minor ▁differences ▁in ▁mechan ics . ▁The ▁fifth ▁and ▁sixth ▁ed itions ▁though ▁would ▁re legate ▁G amma ▁World ▁to ▁that ▁of ▁a ▁Camp aign ▁Setting ▁and ▁require ▁the ▁core ▁books ▁to ▁play . ▁ 5 th ▁uses ▁the ▁Altern ity ▁system ▁which ▁is ▁mostly ▁represented ▁in ▁the ▁book ▁but ▁required ▁the ▁core ▁rules ▁in ▁order ▁to ▁resolve ▁some ▁factors . ▁ 6 th ▁Edition ▁though ▁was ▁fully ▁incomplete ▁on ▁its ▁own ▁and ▁required ▁the ▁d 2 0 ▁Modern ▁rule book ▁in ▁order ▁to ▁play ▁the ▁game . ▁ ▁The ▁sevent h ▁version ▁uses ▁a ▁stream lined ▁version ▁of ▁D & D ▁ 4 th ▁edition ▁mechan ics . ▁Character ▁generation ▁choice ▁though ▁was ▁nearly ▁fully ▁removed . ▁Instead ▁of ▁choosing ▁a ▁character ▁class , ▁a ▁player ▁had ▁to ▁roll ▁a ▁twenty - s ided ▁die ▁two ▁times ▁and ▁consult ▁an ▁accomp any ing ▁character ▁origin ▁table . ▁For ▁example , ▁a ▁player ▁might ▁obtain ▁the ▁result ▁" Radio active ▁Yet i " ▁and ▁gain ▁the ▁powers ▁associated ▁with ▁the ▁" Radio active " ▁and ▁" Y eti " ▁orig ins . ▁Att ributes , ▁mut ations , ▁and ▁skills ▁were ▁also ▁randomly ▁assigned . ▁Two ▁de cks ▁of ▁cards ▁compr ising ▁the ▁core ▁of ▁a ▁Collect ible ▁Card ▁Game ▁are ▁included ▁with ▁the ▁game . ▁One ▁deck ▁represented ▁random ▁Al pha ▁Mut ations , ▁which ▁could ▁be ▁drawn ▁to ▁gain ▁temporary ▁powers , ▁and ▁the ▁other ▁contained