Aquitect's Will

The clever part is what it does to other people's lands. Islandwalk has always carried the same structural flaw: it is devastating against an opponent who controls Islands and completely inert against one who does not, so a Merfolk deck leaning on the keyword has no answer when the table brings Mountains and Plains. This is the manufactured guarantee, a one-mana sorcery that supplies the condition the keyword needs. Drop a flood counter on a Forest and your unblockable corps walks straight through a green deck's defenses; the counter sticks, so the conversion is permanent rather than a one-turn window. The Merfolk clause cantrips, replacing the card whenever you control a single tribesman, which in the deck that wants this you almost always do. Note the asymmetry of the target: it reads "target land," yours or theirs, so it doubles as color fixing or a way to switch on your own islandwalkers, though that is rarely the point. The whole design exists to make a conditional evasion keyword reliable by manufacturing the trigger itself, then softening the card cost when the tribe is online. It is glue built to patch a weakness islandwalk has carried since the keyword first appeared, sitting alongside Spreading Seas and the other Island-conversion effects as the cheapest way to turn an opponent's basics blue.