It doesn't open because you have to find a starfish at the museum and then use it to put it on the offering stone. The starfish is on the face of Poseidon's statue.
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You teleport by the mirror.
go to the castle or whatever and open the door
go to the castle or whatever and open the door
you open the handle and if its locked jump over it!
well you find it in the castle near the mcm and press the brick and a passage will open
You take the sea star and give it to his altar. If you mean his gate in the water, you need hercules to do it.
You get into the earth castle by kiling the samori in front of the gate then open the gate or if you look to the left of the door you can wall jump up into the castle.
you heve to have Hercules break the pad lock off the gate
The key to the gate on Mythology Island in Poptropica is located inside the Tree of Immortality, which is found in the Grove of Temples. You need to solve puzzles and defeat enemies to reach the Tree and obtain the key.
you go to main street with your ticket and you give it to the lady next to the Gate door that is slightly open.
its impossible i don't know so try on your on sucker.ha ha