Silver Surfer, Vol 3, number 75.
This was the 75th issue, and doubtless was intended to be a landmark.
Unfortunately, scripter Ron Marz was not up to the task. The power-mad Morg is an uninteresting villain, utterly monomaniacal, and completely without nuance or conflict. (This is not better illustrated in a later issue, when the heralds and other celestial powered super-beings were captured by Tyrant. Rather than join the other heralds in their struggle against the vastly powerful Tyrant, Morg took the opportunity to continue his vendetta against Terrax, thereby taking both himself and Terrax out of the conflict against the Galactus-level Tyrant. further reducing his own already dim chance of survival.)
The Heralds' collective struggle against Morg was poorly scripted. For some odd reason, the Heralds, for the most part, chose to challenge Morg one at a time. For example, while Air-Walker fought against Morg, Terrax, Nova and Firelord seemed content to watch while Morg nearly destroyed Air-Walker single-handedly.
Nova and Firelord then strike in tandem (making this the only team effort done by the heralds). Morg effortlessly repels Nova, then turns his attention to Firelord, disarming and inflicting a grave wound on him. Again, where is Terrax? Why is Firelord facing Morg without assistance?
Finally, as Morg is about to dispatch Firelord, Terrax issues his challenge. Rather than finish off Firelord, Morg then turns his attention to Terrax. It's very odd that Morg would fail to complete his kill to trade insults with Terrax. Particularly considering Morg's aforementioned single-mindedness.
Morg then faces Terrax, and (as he has done with the previous heralds) makes short work of him. Then as Morg is about to kill Terrax, he is blindsided by an attack from Nova. Which is the first time in this battle that Morg was believably prevented from completing a kill.
The Silver Surfer finally arrives, while Galactus lags behind. This is especially strange, considering Galactus can teleport. Even more bizarre is that the vastly powerful Galactus, who gave the Surfer his powers, moves more slowly than the Surfer.
Nova seems rather quick to claim credit for defeating Morg, despite the help she had from the other heralds. Which makes it seem all the more likely that Ron Marz simply doesn't like Nova. When Morg recovers from Nova's attack, the Surfer only watches as Nova dies, making no move against Morg or any effort to protect Nova.
Another rather unbelievable aspect of this story is the Surfer's efforts to persuade Galactus to remove the power cosmic from Morg. The Silver Surfer claims that as long as Morg is retained by Galactus, Galactus would never know peace as more heroes gather to oppose Galactus.
Why would this line of reasoning persuade Galactus? He has already committed genocide multiple times. He already is the most despised being in the multiverse. Why would having Morg as his herald make this worse for him?
This story seemed very forced and implausible. The improbabilities of this story have already been covered.
Basically, it was an effort to create a landmark story by killing Nova that failed in the storytelling. Consequently, Nova's death seemed more a gratuitous cheap-shot to sell comics than a believable outcome from a well-crafted plot.