Aleister's birthday is August 19, which in many parts of the world would be written as 19-08, an Arc Number for his father, Rourke. Then we learn that Aleister is a clone, which means everything related to his conception was meticulously planned. What are the odds that Rourke intentionally set it up for Aleister to be born on that date?
The Catalyst Idol for Taylor represents Andromeda, the only human among the other animal or mythical creature constellations. It looks like a person in chains, without any determinable gender. This is because the game does not care whether you chose to be male or female. It is also retrieved by diving into the water after it falls from the Cetus' esca. The original Andromeda myth had her chained to a rock at sea to lure Cetus out.
Aleister and Estela are the only Catalysts associated with reptiles, the snake for the former and the dragon for the latter. Meanwhile, Rourke is also associated with another reptile: the hydra, a multi-headed serpentine creature. This symbolizes Rourke being Aleister and Estela's father in different ways: the former is a clone Rourke considers inferior, like the snake being a mere animal; the latter is Rourke's biological daughter he considers superior, like the dragon and hydra being powerful mythical creatures.
In retrospect, the scene from the past in Taylor's Idol vision can be read as Diego talking to himself since Taylor doesn't exist yet. Along the same lines, Diego's Idol vision doesn't have a past because Taylor's absence would be notable.
