Complex sentence: The third is Lorne (aka The Host), who takes the place of The Oracles beginning in season two of "Angel", and who remains one of Angel's most charming and reliable (but not infallible) guides throughout the rest of the series.
Split into simpler sentences: The third is Lorne, also known as The Host, who takes the place of The Oracles starting in season two of "Angel". Lorne remains one of Angel's most reliable (but not infallible) guides throughout the rest of the series.