The League of "8" or simply the "8" - this very description means a lot to any seasoned Mandrake fan & that too rightfully as "8" signifies the one-of-the most dreaded crime-organisation readers experienced in ANY of the comic-strips! They were(or are?) unique on many aspects,,,from their 800-year long crime history which started in the medieval era or those mysterious hide-outs(they had 8 arms around the world like Octopus) up to their chief ,the mysterious 'Octon' who controlled every move of this secret crooked organisation....everything is truly fascinating!! :o)
Mandrake & Co. were accidentally introduced wid this gang way back in the 1965,curtsy Narda's study on ancient history where she stumbles upon clues of an ancient crime-gang ,which everybody thought extinct by now,the league of "8" and she got enough clues indicating that this gang is still alive,,only their pattern-of-crime has been changed over these years!!To make it short,in this way Mandrake/Lothar introduced with a crime-gang and eventually became their MOST dreaded enemy ...
After 1965,M/L duo found many other secret hide-outs of "8" and as their rule,Octon always destroyed their arm(s) when that failed to nab their enemies(precisely M/L!) .In this way the first hand had been destroyed when their members were failed to kill Mandrake & his companions,in the mysterious Island of 8 !!
That was 1968,when a English criminologist,Dr.Dell, visited Xanadu to see mandrake's famous Rouge's gallery and eventually hooked with the description of The League of "8" ...Later she mentioned her knowledge on "8" in one of her seminars & soon kidnapped as like Mandrake once said "after Police - the thing '8' hated most is - publicity" .In order to find out what happened wid their beautiful friend,M/L were also 
kidnapped & brought in a mysterious island of this secret crime organisation!Now it's the first time where one can see the mysterious island of 8 where everything,from the castle to the
garden,is in the shape of their crime-sign i.e. "8" !! This headquarter,the 7th of their arms,was a 8 shaped castle and was filled with the 8 symbols. With help from Inter Intel Mandrake,Lothar & Dr.Dell succeeded to escape from the headquarter ,i.e. the 7th. arm of the league of 8, just in time before their mysterious chief 'Octon' blew the whole headquarter !
In the several other encounters with the league of '8',most of their hide-outs were based on cities/localities ,unlike this hidden mysterious island and eventually this particular encounter(D136:Dr.Dell & '8' ;1968) is MOST thrilling among the '8'-series on this account. In short,a special island of this mysterious-n-ancient crime gang,where everything bears their unique symbol,is more fascinating and also matched with their mysterious attitude in very move!
* Trivia: The panels are mostly taken from a French version of that Daily:D136 ,which published in Indrajal twice as 'Gigantic Octopus(#226)' and 'The Hideous Underworld(V23 N10)' ....Anyway,you will see some panels in this French version which were 'edited' in Ijc wid needless to mention :the awesome coloring used in this strip! :)
