If Mystics are evil and of Satan then why aren't they the ones that are killing everyone?

Because god and satan do not exist.

Capital punishment, or the death penalty, is the killing of a person by judicial process as a punishment for an offense. Crimes that can result in a death penalty are known as capital crimes or capital offences. The term capital originates from Latin capitalis, literally "regarding the head" (Latin caput). Hence, a capital crime was originally one punished by the severing of the head.

Capital punishment has in the past been practiced in virtually every society, although currently only 58 nations actively practice it, with 95 countries abolishing it (the remainder having not used it for 10 years or allowing it only in exceptional circumstances such as war). It is a matter of active controversy in various countries and states, and positions can vary within a single political ideology or cultural region. In the EU member states, Article 2 of the Charter of Fundamental Rights of the European Union prohibits the use of capital punishment.

Today, most countries are considered by Amnesty International as abolitionists, which allowed a vote on a nonbinding resolution to the UN to promote the abolition of the death penalty. But more than 60% of the worldwide population live in countries where executions take place insofar as the four most populous countries in the world (the People's Republic of China, India, United States and Indonesia) apply the death penalty and are unlikely to abolish it in the near future.