Complex sentence: Encountering mechanical bugs there, O'Neill learns from the dying Asgard Thor on-board that the so-called Replicators ingest the ship's alloys to self-replicate and will eventually land on Earth in the search of more raw material.
Split into simpler sentences: Encountering mechanical bugs there, O'Neill learns from the dying Asgard Thor on-board that the creatures are called Replicators. They ingest the ship's alloys to self-replicate and will eventually land on Earth in the search of more raw material.