Tidal Warrior

The verb is the whole trick: a land that "becomes" an Island has its existing land types overwritten, losing whatever abilities those types granted, so this is replacement rather than addition. Pointed across the table, that overwrite is a denial tool: it strands a mana-hungry activated ability that needs a color you have just erased, or shuts off a hue for a turn, and because it activates at instant speed you can do it on an opponent's upkeep before they have laid their answers. Pointed at your own land, the same ability runs in reverse, manufacturing an Island where you needed one (handy when a card cares about controlling an Island, or when you simply need a blue source for a turn). Islandwalk wants this aimed at the defender instead: that evasion checks whether the defending player controls an Island, so editing their manabase, not yours, is what opens the lane. The duration is where the card is held in check. The overwrite expires with the turn, so it cannot permanently break a manabase or hard-lock a player; the repeatable tap stays a tempo tool rather than an oppressive lock. Each activation costs a full turn cycle (the 1/1 body has to survive and untap), the honest price on an effect that would be punishing if it were free.