Enchanted Pixie Dust

Turning into a pixie gives you flight with no fuel gauge and shrinks you down to a single block, which is a genuinely different way to move through a world. Cave systems you would normally have to tunnel through become passable, and the faint glow means you can see a little without holding a light.

The trade is absolute. Using any item drops the form, so this is travel, scouting and building logistics only, never combat. Liquids drag it down hard and honey nearly stops it outright, though a swimming buff cancels most of the water penalty and a couple of options fix all three.

Watch where you land. Dismount into a gap too small for a normal body and the game refuses, retries, then gives up and teleports you, in the worst case all the way back to your spawn point.