'Shh,' I said gently. 'It does not matter. Just rest easy.'

'Tell Arthur I am sorry…' he whispered, and fell to coughing and could not catch his breath. He died, choking on his blood before Myrddin could reach him. 'Go with God, my friend,' I said, and lay his hand upon his chest.

Just as swiftly as it had come, the apparition vanished. The ground continued to drum and tremble for a time, but the creature was gone. Myrddin appeared at my side and bent over the fallen warrior. 'It is Tallaght,' I said as the Emrys stretched his hand towards the young man's face. 'He is dead.'

Some of the warriors nearby repeated this pronouncement, and it was passed along the ranks. A moment later, there came a cry from farther up the trail. 'Stop him!' one of the warriors shouted. 'Someone stop him!'

Glancing up, I saw a mounted warrior burst forth from among the horses. Rhys shouted for the man to stop at once, and several others tried to head off the hqrse, but the rider was too quick and the horse had already reached its stride. He gained the trail at a gallop, and disappeared into the shadows.

Arthur quickly ordered men to go after him, but Myrddin counselled against it. 'It is too late now,' he said. 'Let him go.'

'We can catch him still,' the king protested.

'We have just lost one warrior to the beast,' the Emrys informed Arthur. 'How many more will you risk?'

Arthur frowned, but accepted his counsellor's advice. 'Did you see who it was?'

'No.' Myrddin shook his head slowly.

'I saw him,' I told them. 'It was Peredur. No doubt he has gone to avenge his kinsman's death.'

'The young fool,' Arthur muttered.

'He is God's concern now,' Myrddin said. 'Put him from your thoughts, and instead think how to find your missing warriors.'

Night was hard upon us, and rather than risk losing the rest of the warband in the dark, Arthur decided to make camp and wait until morning. We buried Tallaght's body where he had fallen, and Myrddin spoke a prayer over the grave. I would have liked to do more for the boy, but that is the way of it sometimes. The Pendragon ordered the remaining Cymbrogi to gather fuel for a fire. What with the dense wood all around us, the men had a great heap of dead timber piled up, and in less time than it takes to tell, the first snakes of flame were slithering up the tangle of old branches.

Once the horses were settled, we gathered to warm ourselves and, in crowding close, to console one another. The fellowship of loyal men is not to be slighted; it is a thing of great solace and is therefore sacred. Accordingly, the Pendragon, in ordering the fire, meant not only to warm us, but to help us to restore our confidence, which had been badly shaken. No one could have imagined that it would turn out as it did.

Comforted by the fire, the men began to talk, and some wondered aloud what manner of creature it was that they had driven off; others voiced surprise that they should have chased it away at all. Speculation proved futile and as one suggestion after another foundered, everyone turned to Myrddin, who was squatting on his haunches at the edge of the fire, arms crossed over knees, staring bleakly into the flames.

'Here, now, Myrddin,' called Arthur genially. 'Have you ever heard tell of such a beast?'

At first it seemed Myrddin had not heard the king's question.

He made no move, but continued staring into the red heart of the fire.

'What say you, bard?' the king said, his voice loud in the sudden quiet of the wood.

The Cymbrogi watched in silent expectation as the Emrys, without taking his eyes from the flames, slowly drew the hood of his cloak over his head and rose. He stood for a moment as if entranced by the flames, then stooped and reached into the fire. Several of the Cymbrogi cried out instinctively at the act, but Myrddin calmly withdrew a fistful of hot ashes. Despite the heat, he held the embers in his hand, blew on them, and then gazed upon the coals.

We watched in astonished silence as he held the burning embers in his hand, his face illumined in the ruddy glow. Suddenly he cast the coals back into the flames. He stood for a moment clutching his hand – whether from pain or the shock of what he had seen, I cannot say – then, as if in a trance, he raised his hand and licked the palm with his tongue.

No one moved or said a word as the Bard of Britain took up his staff and raised it over his head. Slowly, he turned to face us. My heart clenched in my chest, for his face was as rigid and pale as death.

The eyes gazing out from beneath the hood were no longer those of a man, but of a preying hawk, farseeing, keen, and golden. Stretching forth his hand, he held his palm level to the ground and, opening his mouth, began to speak. Or perhaps it was some other speaking through him, for the voice seemed to come from the Otherworld.

'Hear, Men of Britain, Valiant Ones,' he said in the strange, hollow voice, 'the Head of Wisdom speaks. Heed and take warning. The Black Beast sent among you this day was but a foretaste of the power arrayed against you. The battle is joined, and every man who would achieve the quest must face many ordeals. Be not dismayed, neither be afraid, but face the trials to follow with all forbearance, for the Swift Sure Hand upholds you, and the Holy Grail awaits those who endure to the end.'

Having delivered himself of this decree, he lowered his staff and sat down again. Almost at once, he began to shake and tremble all over. Thinking to aid him, the warrior nearest reached out and took hold of the Emrys to steady him. Instantly, the man yelped and fell back as if he had been struck by a thunderbolt.

Others reached to help the man. 'Let him be,' advised Arthur sternly. 'It will pass.'

The stricken warrior quickly recovered, and the Cymbrogi set themselves the task of settling the horses for the night before lying down to rest. Though I tried to sleep, the weird events of this fraught day conspired to overthrow my best resolve and I found myself thinking about Morgian instead, and wondering when the next attack would come, and what form it would take.

It was still dark when I awoke. Judging by the deep darkness of the forest, dawn was still very far away. At first I closed my eyes and tried to go back to sleep, but then I heard again what must have roused me: the horses were awake and whickering restively to one another, so I roused myself, thinking to see what might be done to calm them.

The fire had burned itself to a heap of ashes, and I had to stumble over the sleeping bodies of my swordbrothers, waking a few of them, who joined me at the picket with the horses. 'I feel as if I have slept an age,' remarked one of the warriors. 'But it looks as though dawn is still far off.' He gazed around warily. 'Indeed, if I did not know better, I would say the darkness has only increased.'

As he spoke, a thin trickle of fear snaked along my ribs. I raised my eyes to the darkness above, dense and heavy as iron. Others joined us and began offering their observations. Some held that the night had passed and we would soon see the sunrise; more maintained that the time for sunrise had passed without bringing the light.

Before the disputation could become contentious, however, Arthur brought an end to the speculation by putting the question to Myrddin directly. 'Is this the enemy's doing?'

Myrddin hesitated, then glanced quickly at the warriors, who stood awaiting his answer. 'Yes,' he said simply.

The king nodded. 'It makes no difference.' Turning to the Cymbrogi, he said, 'Our swordbrothers should have reached us by now. We are going back for them.' He ordered the horses to be saddled and all idle talk to cease; he commanded torches to be prepared, and once we were saddled and ready to depart, the torches were lit.