When Zhao Hai led his men to check it out, they found a cave on the mountain behind the platform. The cave was very large. They even saw an incomplete teleportation array in the cave. Other than the teleportation array, there was also a defense array. It should be the one they had used before. The defense array was not big, only a formation disk about two meters in diameter.
However, the energy crystals on the defensive array had already been crushed into powder, which was why their protective shield had been broken. As long as they replaced it with energy crystals, this defensive array should still be very useful.
As for the teleportation formation, the people of Silversand Island hadn't finished building it yet, so Zhao Hai and the others couldn't use it yet. However, with this half-completed teleportation formation, it would be much easier for them to build it.