There is a cave at Cruachan. Its small dark mouth yawns at your feet beneath a shroud of hawthorn bushes, and is never lit up by the sun. You can slide your way in, if you dare. The only way is supine on your belly, sinuous as a snake in the thick blackness, or on your back, enclosed so closely that the rock wall brushes your skin as you pass, the weight of the earth pressing on your consciousness, on your lungs, filling you with the fear of rockfalls, of demonic creatures which burst through from the Otherworld, of the terrible Goddess of strife and death we call the Morrigan, of the dread that once inside, you will become trapped, unable to ever return to the surface.
There was no way I was not going in. The mouth of the cave gaped at me, and I watched in trepidation as it swallowed first Treasa, then two more of my companions, and then I plunged in. Now or never.