Shelldock Isle is a rare Land card from Arena Anthology 3 (AA3), collector number 24.
Hideaway 4 (When this land enters, look at the top four cards of your library, exile one face down, then put the rest on the bottom in a random order.) This land enters tapped. {T}: Add {U}. {U}, {T}: You may play the exiled card without paying its mana cost if a library has twenty or fewer cards in it.