(Tidal Stronghold isn't a spell.)

At the beginning of your upkeep, Tidal Stronghold deals 1 damage to target creature you control.

Tidal Stronghold is indestructible. (Destroy effects and lethal damage don't destroy it.)

, Pay 1 life, Sacrifice Tidal Stronghold: Search your library for a Island or Swamp card and put it onto the battlefield, then shuffle your library.