For 10 points, name this empire which predates Islam, whose role in the West African salt-for-gold trade was later taken up by Mali.
This empire's ruler determined innocence with an ordeal called "trial by wood," which saw if an accused person vomited up bitter water or not. This empire gained power when Audaghost, an independent city-state on its border, fell under its rule. This empire was the first in its region to treat all gold nuggets larger than dust as its king's property. After the rule of Tunka Menin here, the (*) Almoravids went south to sack and weaken this empire, whose main ethnicity was the Soninke people. Technically, this empire's name referred to its ruler, who lived in Kumbi Saleh in the 1000s AD. For 10 points, name this empire which predates Islam, whose role in the West African salt-for-gold trade was later taken up by Mali.
This empire's ruler determined innocence with an ordeal called "trial by wood," which saw if an accused person vomited up bitter water or not.
Ghana empire [or Wagadou]