Complex sentence: Katherine was pregnant when the Summers were abducted by D'Ken, Majestor of the Shi'ar Imperium, and her child was seemingly killed when the mad emperor, in retaliation for an attempt by Corsair to escape, stabbed Katherine and killed her.
Split into simpler sentences: Katherine was pregnant when the Summers were abducted by D'Ken, Majestor of the Shi'ar Imperium. The unborn child was seemingly killed when the mad emperor, in retaliation for an attempt by Corsair to escape, stabbed Katherine and killed her.