Following the same celestial trail as Andromeda, the dying Sidereon found himself on a world of abundant matter with which to feed on, seeking to delay his inevitable doom. Having found allies in the Hellbourne (whose lust for destruction almost rivals his own), Sidereon wages an unrelenting campaign to consume the entirety of Newerth, and all those who live on it.
Sidereon is best described as a Tank. While he doesn't have any significant abilities that make him harder to kill (excepting Gravitic Punch), he isn't someone you want to ignore. While he could conceivably do well on his own, most of Sidereon's abilities are created with one main idea in mind: disruption. He's a team player.
Physically, Sidereon appears much like Andromeda, but in a far more chaotic state. He is clad in Hell-forged armor that only barely contains his sputtering essence, ribbons of white-hot energy flaring out from every opening.
Base Damage: 47-59
Move Speed: 290
Strength: 24 (2.5 per level)
Agility: 18 (1.7 per level)
Intelligence: 19 (1.8 per level)
600 Cast Range
Sidereon is a master at manipulating space-time. He creates a short-lived anomaly that pulls in all enemy targets in the AoE to the targeted spot, as well as dealing 120/140/160/180 Magic damage.
Collapse is mainly used as a setup for the rest of Sidereon's abilities. It can force opponents to stay in Gravitic Punch for longer; it can provide an opportunity for Sidereon to circle around and slow enemies with Distortion; and it can provide an excellent opportunity to gather up enemies in a straight enough line to hit them with Fusion Spiral. It's also extremely useful for setting up for heroes such as Magmus or Behemoth who depend heavily on positioning.
Sidereon slams his fist into the ground with enough force to rip space-time, creating a black hole that heavily distorts the area. Enemies within the area suffer 32/38/42/48 Magic damage per second, while Sidereon is healed for 32/38/42/48 healthwhile in the area.
The main use of Gravitic Punch is as area denial. It creates a vast swathe where staying is a bad idea, because the damage does add up. It also provides significant benefit for Sidereon to stay inside, and can be a very important tactical ability when Collapse is used alongside it.
Sidereon's very presence warps gravity around him, and the aftereffects can be felt long after his passing. Sidereon constantly trails a distortion behind him. Opponents who walk where Sidereon last walked within 3 seconds are slowed by 13/16/18/22% for 1 second.
Distortion, like all of Sidereon's abilities, is multi-purpose. It can be used offensively to slow opponents attempting to get away from your team, or to keep them inside of Gravitic Punch. It can also be used defensively, providing Sidereon with a good escape mechanism from chasers (provided Sidereon is good enough at moving to make it difficult for the chaser to not step into Distortion).
600 Cast Range
Unleashing a precious portion of his collapsing essence, Sidereon fires a concentrated fusion beam at a target. The target is stunned for 2/2.5/3 seconds and suffers 200/250/300 Magic damage. Any enemies (except for the initial target) who get caught in the beam are dealt 180/210/230 Magic damage and suffer -2/-4/-6 Magic armor for 4 seconds.
This description seemed like it could be a bit confusing, so to clarify:
Sidereon fires Fusion Spiral at a target, creating a beam with a relatively small radius (think Witch Hunter's Graveyard). It instantly hits the target after being cast. The target suffers Magic damage and a stun. Anything that's caught between Sidereon and the beam's target will be dealt Magic damage and also gain a Magic armor debuff.
Fusion Spiral's main purpose is to punish anyone with poor positional awareness. The damage it does is relatively unimpressive (for an ult, anyways); its main feature is the secondary effects. For the target, they get hit with a lengthy stun, which Sidereon's team can use to their advantage. Anyone who gets caught in the beam suffers a significant Magic armor penalty, which can be exploited by people like Pyromancer/Witch Slayer/etc. to good effect.