Keter means it's difficult to contain, it doesn't mean it's dangerous. it's an easy mistake to make considering Keters are often dangerous. think of the locked box test: if you lock it in a box and nothing happens, it's Safe. if you lock in a box and you're not sure what will happen, it's Euclid. if you lock it in a box and it will definitely escape, it's Keter. if it is the box is Thaumiel. if it doesn't fit in the box and it's about to end the world, it's Apollyon.