i'm behind too, but one thing that i know happened was that knuckles died, and then came back to life in 125 but lost his powers.

I can't recall much of the RTAI arc, but I do remember that they introduced us to Mace, much to Knuckles's displeasure.

Okay guys, I'm here to fill in some of the blanks. I myself haven't read those issues in their entirety, but I know enough of the plot to summarize. As it was brought up first, I'll begin with what happened after Chaos (Green) Knuckles teamed up with the Dark Legion.

What basically happened is that Knuckles and Dimitri worked together in an attempt to rewrite history, sending Knuckles back in time to certain points in Echidnaopolis' past in hopes of creating a better future. Dimitri also seems to have convinced Knuckles that doing so would bring all the Echidnas and the Chaotix back to Angel Island, which the Legion apparently couldn't do because the Quantum Beam weapon they used to do it in the first place was destroyed. Knuckles went back in time to the White Comet's impact on Mobius, Dimitri's attempt to drain the original 12 Chaos Emeralds of Floating Island and lower it back to the surface, and the moment of Edmund's death. Unfortunately, his efforts in all three failed: depending on the event, the White Comet destroyed Echidnaopolis, the Floating Island crashed and was destroyed, or Knuckles became a Robian.

Luckily, none of these failed efforts had any effect on the timeline of Mobius Prime, and Knuckles ended up undoing the Quantum Beam's effects by himself. Dimitri then worked with him to try and form a peace between the Legion and Echidnaopolis-whether he was sincere or just hiding an ulterior motive is unknown-only for Knuckles to fake his own death by taking an assassin's blast aimed at either Dimitri or the Echidnaopolis spiritual leader, the Mitre. Knuckles' daughter Lara-Su interferred in these events, preventing Julie-Su's death by Legion sniper.

Dimitri's failing health left him immobilized and bound to a table, relying on Knuckles to keep him alive. Unfortunately, he was kidnapped by Mammoth Mogul and used to lure Knuckles into a giant Chaos Siphon. Knuckles destroyed the machine, but at the cost of his own life-hopefully, you know what happens from there.

Return to Angel Island worked out like this: Charmy and Saffron arrive in Knothole, joining up with the Chaotix after Robotnik destroys their home city. A transmission from Angel Island arrives, informing them that Locke has been imprisoned by Robotnik's Dingo allies. Knuckles, despite being powerless, joins the Chaotix and Sonic in an assault on the island, liberating several Echidnas. Sadly, Knuckles finds himself dealing with yet another unwanted aspect of the Ancient Walkers' plans for him: the Echidna people hail him as the Avatar, a hero who is destined to return from death and deliver Mobius from its suffering.

While still trying to cope with this, Knuckles and the gang run into the Dark Legion, who are now commanded by Lien-Da and her advisor Dr. Finitevus. Lara-Le and Wynmacher are also revealed to be with them, at which point Knuckles is introduced to his baby half-brother Kneecaps. Lien-Da reveals that the Brotherhood, minus Locke, disappeared after defeating Robotnik's attempt to seize control of the Master Emerald, which the Dark Legion then took charge of at Locke's request. Knuckles then finds that being in the Emerald's general vicinity weakens him and causes him great pain, to the apparent gratification of an observing Archimedes.

Leaving Finitevus, Remington, and a number of others to guard the Master Emerald, the Chaotix and the Dark Legion go to save Locke from the Dingoes. They're reunited with Harry, the Chaotix's Dingo ally, who is revealed to be a spy for the Echidna cause. After defeating General Kage, the Dingo commander, Knuckles and co. learn that Robotnik has recruited Knuckles' old enemy Hunter and sent him to capture the Master Emerald. Using his Chaos Spear, Hunter sends a number of Angel Islanders to Robotnik's Egg Grape Chamber, but Dr. Finitevus is either ignored by him or leaves before Hunter can attack him.

Knuckles and Sonic return just in time to fight Hunter, but the Emerald continues to leave Knuckles feeling weak. But before Hunter can seize the Emerald, Knuckles evolves into his Super form, challenging Hunter and defeating him by throwing him off the island. After powering down, he learns that he's regained all his powers. Locke then asks him to remain on Angel Island, but Knuckles refuses, having decided that his duties are to Mobius as a whole, not just Angel Island, which leads to their future disagreements. The Chaotix then return to Knothole, unaware that Remington and many other prisoners have been taken captive by Robotnik.

Hope this was informative, and I apologize if it's too long.

Thanks, that cleared up a lot of my confusion.

I just have one last question: How does get in his chaos form? Is he able to do it at will?

And another one: How come Knuckles and Shadow rarely/never chaos control. You never see Knuckles warping and Shadow has only done this a couple times. And Shadow was only shown using chaos blasts once (in 25 years later).

Knuckles only turned "green" due to saving his own life. He did it unconsciously--it wasn't a conscious decision. So, no, he's never been shown to be able to do it at will. In fact, once it happened, he couldn't turn himself back to being his "normal" red fur color (even though he was colored "wrongly" in one issue in the 90s after the change).

Knuckles doesn't use chaos control in the games, so that's not expected to happen in Archie either. Knuckles only can "warp" with the Guiding Star Gem in Archie. I don't pay attention to the games as much as I do Archie, but I'm under the impression that Shadow needs a chaos emerald to do chaos control. I could be wrong though. ;p

I could've sworn Shadow was warping in STH #124/125

What happened to Dimitri between the time Knuckles saved him and Sonic #171?

He became a head bubble.

Never mind.
100th Post!

To explain Toby's comment more clearly, Dimitri's health got so bad that in order to keep him alive Dr. Finitevus had to take him apart, preserving his head-aka his brain-in a floating orb.

As for Chaos Knuckles, Knuckles hasn't shown himself to be able to do it at will, and he's only done it once. Presumably, from the past of Mobius: 25 Years Later, we can presume that he may be able to do it again somehow, but only time will tell.