Corrupted Wood can be found mainly on the Corruption layer, which currently is the deepest layer of every Creativerse-world.
On many of the currently newest template Worlds RW 4-8 a few blocks of Corrupted Wood looking like trunks of thin trees are floating over the surface, like over Water or Grasslands; however they are rare findings.
Corrupted Wood can be used as a Fuel for Forges; 2 blocks will be needed for each process (of melting or hardening), it burns very fast and such is nearly the best fuel in Creativerse. Also Corrupted Leaves (you'll need 4 blocks of those each though) are fuel of the same high quality.
Corrupted Wood can also be "created" by players too, however only by throwing Corrupt Bombs at uncorrupted Wood, because since patch R43 (the "Welcome" update) common uncorrupted Wood can no longer be corrupted by placing solid corrupted blocks next to blocks of Wood nor by touching Corrupted Water.
Since there are usually nearly no Caves that lead from the surface as far down as the Corruption layer, you can only reach this layer by digging downwards (by using the according Power Cells needed for mining through each layer). The deeper you will dig, the harder the rocks will be that the layers are made of, and the harder the survival will be there.
Corrupted Wood forms long strands of roots all over this ceiling, with occasional small corrupted trees hanging down from it like lanterns (that don't glow), adorned with Corrupted Leaves.
On the ground of the Corruption layer more strands of Corrupted Wood form a net of roots, often even under Corrupted Water. Small corrupted trees grow from them too, and here or there several long thin trunks of Corrupted Wood connect the ceiling and the ground.
You can purify Corrupted Wood like any other corrupted block by throwing Purification Bombs (7x7x5 blocks max. will be purified) or by placing Healing Beacons. By this Corrupted Wood will turn into Cragwood, and these common wood blocks can be harvested without requiring any Power Cells.
Players can turn every block of Wood (not Logs though!) into Corrupted Wood by throwing Corrupt Bombs at Wood blocks. To craft these Bombs, you'll need Corrupted Stone, Corruption Dust and even some Lumite. Since update R39 these Explosives will only corrupt 5x5x5 corruptable blocks at max.
Cragwood turns into common Corrupted Wood when being hit with a Corrupt Bomb. Ashenwood turns into Corrupted Ashenwood when being hit with a Corrupt Bomb. Elderwood turns into Corrupted Elderwood when being hit with a Corrupt Bomb.
Parchwood, Shorewood, Autumnwood, Wildwood, Weepwood will at first be transformed into their corrupted counterparts by Corrupt Bombs - Corrupted Parchwood, Corrupted Shorewood, Corrupted Autumnwood, Corrupted Wildwood and/or Corrupted Weepwood.
If purified again without picking them up, they will all return to their uncorrupted former state and into their original types of Wood again.
However as soon as you'll pick up blocks of Corrupted Cragwood, Corrupted Parchwood, Corrupted Shorewood, Corrupted Autumnwood, Corrupted Wildwood and/or Corrupted Weepwood, they will all turn into ordinary Corrupted Wood in your inventory/bag.
And this Corrupted Wood, if placed again and purified, will then ALL turn into Cragwood instead of into their original wood types.
When creating arenas from Corrupted Wood, all kinds of Corrupted Creatures can spawn there as soon/as long as it is dark, and occasionally even rare Diamond Treasure Chests. Corrupted Leafies will spawn even better when Corrupted Leaves are close by and Corrupted Rocksters will spawn easierly when liquids are nearby.
Corrupted Wood is flammable (as are Corrupted Leaves), but will not easily catch fire. You will either need a Fire Bomb or liquid Lava to make it burn, and the fire will not spread easily nor far to other blocks of Corrupted Wood (or Corrupted Leaves) from where it initially started.
Fire can still spread "well" onto more flammable materials; like uncorrupted Wood, Leaves and the like, but also many building-blocks crafted from Wood and/or Leaves might catch fire easily, and Tar is the easiest ignitable substance of Creativerse.
Fire cannot be extinguished by using liquids, but it can be stopped from spreading by claiming the area and making sure that the claim (advanced) option "fire sim enabled" is disabled (by default). Fire Bombs will have no effect on these claims either.
It is also possible for owners of the gameworld (F2P players included) to toggle the spreading of fire on a whole gameworld in the basic world options ("edit world" and "disable fire spread"). Another option to stop fire from spreading would be to create forest aisles/swaths wide enough so that the flames cannot leap over.
Corrupted Wood does not regrow nor spawn all by itself after the gameworld has been created. However in earlier versions rare bugs have been reported of wood appearing corrupted and then "purifying" itself again after relog. Also sometimes blocks that have been corrupted by corruption spreading were reported to return to their former state for unknown reasons. These issues should have been solved with update R43 though.