Complex sentence: Aru kingdom maintained close cultural and trading relations with their kin in the hinterland--the Karo people of Karoland-at a time when they still practiced a native form of animism and paganism, which included a notorious practice of ritualised cannibalism.
Split into simpler sentences: Aru Kingdom maintained a close cultural and trading relations with their kin up in the hinterland--the Karo people of Karoland. By that time, the Karo people still practiced a native form of animism and paganism, which include a notorious practice of ritualised cannibalism.