After slaying almost all of Tuifeai's troops, some having run off, they left one alive to report back to Tuifeai that they were here to have him taoiseumu ("cooked in an umu").
After defeating many of Tuifeai's troops, some escaped, they left one alive to report back to Tuifeai that they were there to kill him as a ritual sacrifice ("cooked in an umu").