Short answer: William is still alive in Invincible (both the comics and the animated series), but he gradually becomes less central to the story as the focus shifts to galactic‑scale plots and other characters.

What happened to William in Invincible?

In the comics

  • William starts out as Mark Grayson’s best friend and a regular human with no powers, mostly used as a grounded, comedic, and emotional support character.
  • He discovers that Mark is Invincible fairly early on, after putting two and two together during an attack at Upstate University, and promises to keep his identity secret.
  • Over time, he has his own small arcs: college life with Mark, a short relationship with Atom Eve, and reacting to how Mark’s superhero duties keep pulling him away.
  • As the comic shifts more into cosmic wars, Viltrumite politics, and Mark’s family, William’s role shrinks; fans note he is “last seen” around the time he helps Mark and Eve move into their new house (around issue 96), after which he basically fades from the narrative rather than dying in some big moment.

In the animated series (so far)

  • In Amazon’s Invincible show, William is again Mark’s close friend from high school, openly gay, and used as a supportive but sarcastic presence who grounds Mark’s normal life.
  • He plays a key role in the Upstate University/Rick Sheridan storyline: he’s smitten with Rick, is devastated when Rick is turned into a ReAniman, and briefly blames Mark for not helping sooner.
  • The show emphasizes that William both supports Mark as a hero and feels hurt when Mark’s double life damages their friendship, mirroring the comics but with more focus on his LGBTQ identity.
  • As of the latest episodes discussed online, William is still alive and on good terms with Mark, covering for him at college and trying to help Rick cope with trauma, but he isn’t in every major plotline, which has led some fans to worry he’ll drift into the background just like in the comics.

Why he seems to “disappear”

  • Once Invincible moves from high‑school/college drama into full‑on alien empires and multiversal threats, side characters like William naturally get less page and screen time.
  • Some viewers and critics argue the show risks reducing him to a “gay best friend” who pops up for emotional beats but doesn’t get a fully developed arc of his own, especially compared to the comics’ longer runway.
  • On the page, he gets a quiet send‑off (helping Mark and Eve settle into their new life); on screen, his long‑term fate hasn’t been fully shown yet, but the pattern from the source material suggests he’ll remain important emotionally while not being central to the big cosmic storylines.

Fan discussion and “latest news”

  • Forum and Reddit discussions often revolve around whether William will “fade into irrelevance” like in the comics or be given more development and screentime in the show’s later seasons.
  • Official teases, like the Season 2 William redesign shared on social media, show that the creators still consider him part of the ongoing cast, even if he isn’t in every big battle.

TL;DR: William doesn’t die or vanish in a twist; he slowly moves from front‑and‑center best friend to a more background, emotional‑support role as Invincible grows more cosmic, especially in the comics, while the show is still deciding how far to take his arc.

Information gathered from public forums or data available on the internet and portrayed here.