The League of Assassins is an international secret society dedicated to mastery of the various means of murder and assassination. For a price the League will carry out assignments from other parties to kill individuals designated by those parties. At present the League appears to be under the complete control of the aged Oriental martial arts master known only as the Sensei (see Sensei).
Apparently the League was once part of the worldwide criminal organization headed by Ra's al Ghul (see Ra's al Ghul). The Sensei once spoke of himself as the "powerful fang which protects the head." It would seem, therefore, that Ra's al Ghul intended the League to protect him from his enemies and to strike out against them.
Although the Sensei held great power within the League, its president was Dr. Ebenezer Darrk, who apparently was in charge of dealing with those people who wished to hire the League's services.
To enter the League, one must carry out a successful assassination. For his own intitiation test one of the Sensei's pupils, a man known only as the Hook, killed circus aerialist Boston Brand but Brand's twin brother, Cleveland, later impersonated Boston and carried on his act [How come nobody every told me Boston Brand has a twin brother named Cleveland?! I'm assuming his parents traveled a bit and named the kids by the city in which they were conceived.]. Thinking that his pupil had failed, the Sensei killed the Hook in personal combat.
Boston Brand's ghost continued to exist on the Earthly plane as Deadman (see Deadman) and together Deadman and the Batman (see Batman II) were able to thwart the Sensei's attempt to destroy the hidden mystical land of Nanda Parbat within the Himalayas.
The Batman later thwarted attempts by the League to kill two shipping magnates, and in the process encountered Dr. Darrk. Darrk had a falling out with Ra's al Ghul, and in retaliation kidnapped his daughter Talia (see Talia). The Batman rescued Talia, and Darrk was killed.
Later, seeking vengeance on the Batman for the Nanda Parbat affair, the Sensei sent the archer Merlyn to kill him. Merlyn failed and quit the League rather than pay its price of failure, which is death [Seems like an intelligent career choice.].
Under the Sensei the League began acting independently of Ra's al Ghul's control. It is suspected that Ra's convinced the Sensei to have Kathy Kane, the former Batwoman (see Batwoman) killed. Ra's then told the Batman that the Sensei was responsible, in the hope that the Batman would defeat the Sensei and his followers so that Ra's could then reassert control over the League. During this time the brainwashed Bronze Tiger (see Bronze Tiger) served the League, but he left the organization after the Sensei turned against him.
Although the Batman did indeed fight against the League to avenge Kane's death, he did not capture the Sensei. The League of Assassins has now severed all ties with Ra's al Ghul's organization and acts as an entirely independent society.
First appearance [All these changes in format are going to make it look like I was careless in my transcripts whereas I'm trying to just type them as I read them! Like how this entry refused to capitalize "the" in front of Batman. Or how "appearance" just now wasn't capitalized. Also I might miss some commas here and there because they use them oddly and sometimes the print is a bit faded and I can't quite tell if they put in a comma or not.]: (Sensei and League of Assassins) STRANGE ADVENTURES #215, (Dr. Darrk) DETECTIVE COMICS #406, (Merlyn) JUSTICE LEAGUE OF AMERICA #94