I pretty sure he evil, my theory on the story is that this setting takes place during the age of the ancient humans, the ones alive when the forerunners were. All I us guardians tripping on acid and inside the "traveler" is actually the primordial.. The one that said he was one of the previous species ... But in reality he is a grave mind in that time stasis capsule. This is near the humans end, where the humans make a pact with the flood in order to survive, (long story) the "hive" still attacking us even though we really on same side is to fool the other enemies.