A boy with dark hair, pale skin and an aviator jacket stood completely straight before a dark throne. He had been petitioning for some hours, as much as time had any meaning here.

Nico gave a deep sigh. "You still refuse to help?"

The cavernous hall ensured even these fairly quiet words echoed and reverberated till they became devoid of all meaning. It was a strange room, to guess the dimensions would be impossible. All that was clear was that it was focussed on the throne at one end. All else was needless decoration.

A dark figure on the dark throne, fanned by shadows, framed in night, sneered condescendingly. "My siblings have made it clear I am unwelcome on Olympus. I won't interfere in their business." Lord Hades looked down on his son with disdain. Loneliness does not breed compassion, "Myself, the Lady Persephone, Demeter and you, my son, we shall be safe here in Hades. Let the surface world sort itself out." He waved an uncaring hand, dismissing the subject from his attention.

Nico nodded to himself, then looked up to hold his father's gaze. "Very well. Then I must leave you to return to New York." Nico swivelled on his heels and turned to face the open doors of the throne room, framed by torches glowing with a sinister green flame. He began to walk towards them.

The doors slammed shut.

The torches were extinguished.

Hades drummed his fingers on the arm of his throne as he spoke. "Nico, you shall remain here. Such is your father's will." His voice was low now, and silky smooth. "Do not defy me this time, you will not find it pleasant." Hades rose from his throne, his dark aura particularly menacing, and the souls of his cloak moaning in distress.

Nico kept walking the long hall. "I have a sword, my lord, and if you will not help then I must." His hand went to his sword's hilt, and remained there as he continued.

Hades' voice rose "If you disobey me in this Nico, you shall know my wrath."

Nico's pace remained slow and determined, his voice level. He did not look back. "You can't stop me father. I know ways even you won't follow."

"Go and you will not be welcome here when you retreat from your lost cause, little hero." That last phrase was spoken with such utter scorn that even the shadows faltered for a second.

On the walker however, his words made no visible impact. Nico kept walking.

"I'll blunt your sword."

His pace did not change

"Break your shield"

No answer.

"No dead from my domain shall answer your summons!"

Nico had reached the door.

"I'll smite you myself if I have to!" This was said with enough force to shake the throne room, the very Underworld itself echoed with Hade's terrible anger.

Nico spun round, the fury of Tartarus in his eyes.

"Very well father. Break my weapons, I have hands and teeth, I'll go alone and unarmed, so be it!"

The cavern echoed faithfully. The torches sprung back into life with a brilliance before bereft.

The shadows at the walls shrunk back, afraid.

"You have no prison which will hold me. Maim me, so I'll crawl. Kill me, so I die." Those last three words were slow and deliberate. "You will not deter me this time and nothing you can possibly say could frighten me more than the thought of leaving my friends to fight Kronos alone." He turned away again, then hesitated before turning back "And hear me now father, remember my words: If Olympus falls, Hades will be next."

With that the doors flew open, he stormed from the throne room vaporising any guard unlucky enough to be in his line of sight. The doors closed behind him with the clang of an army bashing their shields, and the last of his echoes faded into the darkness.

The silence in his wake was unusual, even in Hades. Not even Demeter said a word as the ash and dust slowly fell to the ground.

Everyone stared at the Lord of the Dead. It had been a long while since he had looked this angry, this furious. They awaited the inevitable explosion.

Instead, he laced his fingers together, his expression blank. He turned his face to the floor, eyes closed.

After what seemed like an eternity, he raised his head.

"Ready my chariot. It seems we are going to war."