I'm assuming, for this first part, that your characters either fail the DC (1d20+48) Spot check to see Damien, and/or that they cannot see Ethereal creatures. He's only Ethereal for about a round, during which he moves into the center of everyone.
Damien makes a Sense Motive check against everyone present: (1d20+45)
And a (less impressive, but still good) Diplomacy: (1d20+32)
There is a faint flicker of shadow in the air, and a cloaked and hooded man steps into view. He stands in the center of the assembled personages, and it is not immediately apparent where he came from; there are no pillars near him, nor any other means of concealment. His sudden appearance is casual and quiet, and after a moment he lifts a hand to raise the grey hood of his cloak.
He is clearly a strong and grown man, but he is just as clearly young; his face shows little sign of lines or weathering, and he has yet to fully lose the slimness of youth. He bears a long, heavy blade at his hip, but in his hand he holds nothing but an old, hand-carved quarterstaff, its end blunted from many travels.
"My name is Damien, Master of the Nine. I am honored, Agamemnon, that you would deign to place my name among the great living legends of the sword, and because of that honor I feel compelled to speak. I am known for my blade, but also, I hope, for my mind and my wisdom." He looks to Berenike, his eyes inquisitive and bright. "I has witnessed the horrible occurrences you speak of with my own eyes, King, and yet I still believe that violence may not be the best answer. I propose something a bit radical, sire; I say that if there is a war brewing between Mankind and the Gods, then we should speak to them to understand their intentions."
He opens his arms wide, casting his voice out to the leaders of humanity. "I do not mean that we should pray to them; the time for prayer is past. I mean that we should travel to them, to Olympus, and speak to them face to face, as equals. And if they would strike us down for such an act..." He trails off, and he puts away his staff, the long oak shaft vanishing into his cloak. He draws his sword, a masterpiece of adamantine and magic, the blade humming with quiet power. "If they would strike us down for such an act, they will find us to be closer to their equals than they may suspect. Ares taught me to hold a blade, but he is my master no longer. If the god of war would turn his blade on humanity, than I will show him how far I have come."
Damien looks to the assembled heroes, his eyes hard and his voice strong. "We cannot just run around here on Earth, trying to put out the fires of calamity as they are started. That is a loser's battle, and we will die by attrition and chaos without ever understanding why. We must speak to the gods, or we may as well cut our own throats. Who here has the strength and the gall to stand by me? And, does any man or woman here see a better solution to our lack of understanding?"