I looked into the Lernaen multi-headed Lumi. Deadgrim 3 seems to be the easiest way to get ahold of immunity to death effects. Immunity to disintegrate is much more difficult---it doesn't seem to be possible as an extraordinary ability. It looks like the proof against transmutation armor ability or Improved Bind Vestige[Haagenti] addresses this although a vulnerability to antimagic field remains.

Even that isn't perfect due to some non-transmutation non-death will-or-die effects like Finger of Expulsion (Dragon #330).