Achlys, also known as Akurisu, is a large island within the Blood Sea. In fact, it is widely considered to be the largest island on Abmarah. It marks the south-eastern edge of the Cometfall Sea (Suiseikai) across from the northwestern island of Cinohshima. It was created due to the uplift caused by the impact of the Cometfall in 1E977.

Largely tropical and hiding an intense arcane power, the island has long been considered cursed and full of monsters. It is one of the largest uncharted areas on Abmarah, and there is only one permanent settlement on the island called Issap. After the curse on the Cometfall Sea was 'lifted' during the events of Curse of the Blood Sea, the Cinoh Shogunate laid claim to the entire island and has slowly started to colonize its northern tip. Superstitions still reign supreme though, and many still believe it to be cursed due to its origin.