Blight
It can also be spawned from the skull explosions of the Wither.
Stage One
This is the earliest stage of Blight when it spawns from the beacon, or replanted use.
Stage one will advance to stage two, when it comes in contact with a water block on the same level. Water above the blight will turn it back to dirt.
Stage Two
Stage two is much like Stage one, except with a darker green on top.
Stage two will advance to Stage three when it comes in contact with a lava block on the same level. Lava above the blight will turn it back to dirt.
Stage Three
Stage three has a darker top than Stage two, and the sides begin to show the growth of roots. Stage three is able to progress vertically, allowing it to grow under dirt exposed to air.
Stage three will mature to stage 4 (Mature Blight) when it comes near an obsidian portal.
Stage Four/ Mature Blight
Mature Blight is a threat to be concerned about. It spreads at a very fast rate, killing all living plant life in its path. It is able to spread to any adjacent dirt blocks, however it cannot jump blocks.
When mined, it returns Mature Blight, unlike the previous 3 stages, which give back only Stage one blight.