raywest

Question: What are the names of the three sisters?

Answer: According to Riordan Wiki on Fandom, they are the Grey sisters, Anger (Deino), Tempest (Persis or Perso), and Wasp (Pemphredo). They are the daughters of minor sea gods.

raywest

Question: What I don't get is that if Thalia's tree had the barrier active all along while Luke, Annabeth, and Grover were kids, in the first film, how was the minotaur able to approach close to the entrance of the camp without being prevented?

Roman Curiel

Chosen answer: Thalia's tree was poisoned, weakening it, and leaving the camp vulnerable to attack. The quest for the Golden Fleece was to provide a cure.

raywest

Answer: Because the barrier prevents the monsters from entering the camp, not from getting close to it. It's the reason why after Percy used the fleece to strengthen the barrier, Luke and Kronos' army used the labyrinth to bypass it.