Be very careful when you treat characters like how your planing to do, killing main characters can be a great way of telling the player that things have hit the fan. But, it must be done perfectly to work. the death needs to have meaning, not in the "noble sacrifice" kind of way, but in both literary meaning and having a purpose within your universe. lets say for example, the government is actually hiding the fact that they need the war to maintain economic stability. Your main characters find out about this and are executed to keep them quiet. Their death was needed in order to keep the conspiracy going and to add impact to a major plot twist. This is a pretty cliched example a would't suggest using it, but it gets my point across.
on a side note, don't make you're main characters your going to kill off one-dimensional. If you really want their deaths to hit home, you gotta make the player care about their deaths. Do you think Mordin Solus' death would have mean't half as much if he was just another red shirt?
on a side note, don't make you're main characters your going to kill off one-dimensional. If you really want their deaths to hit home, you gotta make the player care about their deaths. Do you think Mordin Solus' death would have mean't half as much if he was just another red shirt?