Aercloud (The Aether)

Aerclouds are commonly found in long strips, separate from the land.

They exhibit curious properties. Firstly, mobs and items slowly sink to the lower surface of an aercloud block, instead of the upper one. You still only jump 1 block from the bottom surface, but you can place aerclouds underneath you if you jump. You cannot walk into an aercloud that is placed at head height. They tend to negate fall damage, but not reliably. More experimentation is needed in that context. You can also craft a parachute with aercloud.

Oddly, Aerclouds do cast shadows, and they can stop projectiles. Standing on the bottom surface of an aercloud, mobs and you cannot jump into an aercloud from below.