I sort of like the blood idea; but only to help get the real thing started.
Let's say they are hungry enough to kill and either threaten one of the animals and do damage or the animals attack each other. The damaged one takes refuge in the cauldron and when they finally check on it they find it feasting.
They think its the blood and they do all sorts of bloodletting to no avail.
Perhaps somewhere along the line the frustration builds till one of them attacks the other and that one grasps the cauldron thinking that the animal has been protected all this time while it was there and they claim refuge with the belief that they can't be hurt while they touch the cauldron. This works and they get food so they all think that they just have to have faith the cauldron will provide without realizing that the cauldron in truth is not a cauldron of plenty but one of dependence. It slowly works at making them dependent up it by building a false confidence that it will defend, protect, and feed them.