Minecraft wiki entry for Development_versions, associated text: Found in the Nether, generating 4 blobs per chunk between y=27 and y=36.
It has a similar frequency to blocks like andesite in the Overworld.
Crafted using four magma cream.
Mobs and players take 1 damage every second while touching it, similar to a cactus.
Unlike cactus or fire, this block doesn't destroy items that touch it.
If the player is sneaking, wearing Frost Walker–enchanted armor, or under the Fire Resistance effect, it does not take damage.
If the player dies by standing on it, a new death message will appear: "player discovered that floor was lava".
If the player dies by the block, but after being damaged by a mob or player, the death message will be: "player walked into danger zone due to entity".
Removes water blocks on top when randomly ticked.
It produces smoke particles under the rain.
It emits as much light as it receives from other sources.
e.g. A magma block next to a torch will emit light at level 13, as that was the light level it received from the torch.
If the torch were to be removed then it will search for the next brightest source of light; if no source is found then it will not produce light.