Lyric discussion by forever smacked 

Cover art for Iridium lyrics by Dark Tranquillity

Let the horizon lead Onto the ether of the night Draped across the burning heavens Flying homeward like a bird of the soul

Shattered into a million brighter stars Each flare unique and rare Scattered across forever Out from creation's core An end beyond compare Iridium

As SassuWunnu suggested this seems to be about the "big bang" up until the line "Iridium". Which is a metal of rarity and similarities too Plutonium. The only thing that doesn't fit in is "An end beyond compare" as most of this part talks about a beginning if indeed it is written about the "big bang".

Now is the time to leave We lie awake, we stand afire At the edge of the world Above a myriad of light Below the mantle of the stars And strangely they fall

Here, its confusing because usually the "mantle of the stars" is above us. So it seems he is talking about something between the stars and a infinite light/lights. (Myriad being an infinite source or large number of what its talking about). "Strangely they fall" suggesting that the stars fall from under where this person is positioned, or could be that they are moving upward away from them, causing the stars to have a "falling" effect.

Shattered into a million brighter stars Each flare unique and rare Scattered across forever Out from creation's core An end beyond compare Iridium

Shattered into a million brighter stars Each flare unique and rare Scattered across forever Out from creation's core An end beyond compare An end beyond compare Iridium

Or it could be about a large meteorite that was shattered into a million pieces which race across "forever (universe)" landing in different parts causing it to be a rarity (as mankind sees it anyway). I don't know, just trying to spark ideas haha