Heat Melts Cube (lost unreleased Eazy-E diss track; existence unconfirmed; 1993)
Eazy-E was an American rapper based in Compton, California, and was mostly active from the mid to late 1980s until his untimely death from AIDS in 1995. During this time, he recorded a number of albums/EPs, both solo and with his fellow bandmates N.W.A., whom broke up in 1991.
Perhaps Eazy's most notorious track he ever recorded was the track "Real Muthaphukkin G's" (also known as "Real Compton City G's"), which dissed Dr. Dre, Suge Knight, and the entire Death Row record label. What's surprising is that Eazy-E never recorded an entire diss track against Ice Cube, who dissed Eazy (and the rest of N.W.A.) on "No Vaseline". It's possible this album was never released due to a reported reconciliation.
This article covers the history of the "lost diss track".
Timeline
In 1991, N.W.A had finally broken up after rumors of in-fighting due to payment issues and creative differences. In this year, Ice Cube released his diss track, No Vaseline, on his album "Death Certificate" (listen here).
In 1993, after being dissed on Dr. Dre's album "The Chronic", Eazy-E released his own diss track, entitled "Real Muthaphukkin G's". The entire EP it was released on, It's On Dr. Dre. The diss is considered one of the strongest in the history of hip hop music. (Listen here)
What's strange is that there are no released tracks in which Eazy-E directly disses Ice Cube, which is strange given that Ice Cube during the early 90s was quite critical of Eazy-E. It's been purported that Eazy-E decided not to release what has been reported to be an entire Ice Cube bashing EP, because the two reconciled before Eazy's untimely death.
Post Eazy-E Death
In 2006, a user on the Eazy-E CPT forums reported that there was supposed to be an entire EP dedicated to dissing Ice Cube, but it never was released, likely due to reconciliation. It was said that Ice Cube had listened to it and left the studio in tears, and DJ Yella is still in possession of this track. It's been purported that the EP was titled "Temporary Insanity", and the lead track would have been titled "Heat Melts Cube", and would've been even stronger compared to "Real Compton City G's".
In 2011, a Youtube User named Andy Phill released what was purported to be parts of the lost song, titled "When the Ice Crumbles". ([https://www.youtube.com/watch?v=_vGHxSUJN2k Listen here)
In 2014, in a HipHopDX interview, DJ Yella vaguely talked about the diss track, neither conforming nor denying its existence. He simply said he was in possession of an Eazy-E diss track, but not explaining further. He did confirm that the supposed leak was fake, saying it was parts of an interview put over a homebrew beat.
Current Status
It's next to never that the lost Eazy-E diss will be released, likely out of respect. It's unknown whether the track might have leaked outside of DJ Yella, and where the track may exist.