Anagami are Slayer monsters located on the Aminishi island in The Arc region. While not assigned as slayer assignments normally, they may be killed on a contract from Ling or Sojobo for Slayer experience and chimes.
Anagami require a Slayer level of 90 in order to kill. They are enlightened Seiryu monks and unlike their weaker brothers, the Sotapanna and Sakadagami, do not use any abilities. However, they do have an adrenaline bar which they utilise and once the bar is filled, will unleash a lightning attack, dealing 25% of the player's maximum health in damage. This attack can be avoided by simply moving out of the way when it is performed.
In Buddhism, the Anāgāmi are those who are enlightened beyond the sakadagami.
Anagami and Arhat more closely resemble Chinese dragons, unlike other Dragons on RuneScape which more closely resemble the Western type of dragon. As such, the spirit dragons likely have no connection to the Dragonkin and instead derive their form from that of their master Seiryu.
With the release of nightmare creatures, there was a bug where killing Anagami would count towards the nightmare creature task. This was fixed on 19 December 2016.
^ abJagex. Mod Stu's Twitter account. 26 July 2016. Mod Stu: "I've checked @JagexRowley's code and confirmed spirit dragons are 1 in 16/32/64."