The Erebus has a veritable plethora of flora and fauna; the same goes for fungi.
As you'd expect, all mushrooms found in the Erebus can only be found in Fungal Forests, with the exception of the rare vanilla giant Red Mushroom, which can be found in other biomes. All mushrooms in the Erebus have identical usage, except for Terpsishrooms and Glowshrooms.
In the Overworld, most of these mushrooms can only grow on Mycelium, regardless of light level.
Tangled Stalk Edit
These mushrooms have long, intertwining stalks topped with brown caps. When placed, they sit two blocks high. They cannot grow on Mycelium, but they can on Dirt and are not hindered by light levels.
Using Bone Meal or Compost on Tangled Stalks will not grow a giant mushroom; instead, the Tangled Stalk will drop another Tangled Stalk from itself onto the ground. This is an excellent way to gather mushrooms for any recipes that require them.
Dark Capped Edit
With a dark blue-grey stalk and azure blue cap, these mushrooms are, how you say, "dressed to impress". They have no special recipes that they are required in, but can be grown into a giant mushroom through use of Bone Meal or Compost.
The giant variants spawn naturally in Fungal Forests, and have blue-white stalks that appear scaly, with blue-black caps that have quite a soft-looking fibrous underside.
High Capped Edit
A sibling mushroom to the Tangled Stalk, High Caps are two blocks tall with a very large cap. They cannot be placed on Mycelium, only on Dirt, and are also not hindered by light levels.
When Bone Mealed or Composted, they will drop another High Cap, just as Tangled Stalks drop another of themselves.
Kaizer's Fingers Edit
A rather odd mushroom, Kaizer's Fingers' feature slightly blue stalks topped with red caps in the shape of a hand. Their giant variants, as of the current version (0.4.7), can only spawn naturally, and cannot be grown by a player, even with Bone Meal or Compost.
Sarcastic Czech Edit
The name of this mushroom alone is quite strange, however the shape is a bit more confusing. It is unknown why Sarcastic Czechs are called this, but the mushroom itself appears to be yellowish stalks topped with caps topped with more stalks and caps.
When Bone Mealed/Composted in a 2x2 pattern (i.e. you'll need 4 Sarcastic Czechs), they grow into their giant version, showing in a far more pronounced way their "branching" pattern.
Grandma's Shoes Edit
Another oddly named mushroom, Grandma's Shoes are an off-white stalk topped with a dark green cap. They can be grown using the usual methods when placed in a 2x2 pattern, resulting in a very tall (~12 blocks) mushroom.
Dutch Cap Edit
Tan-coloured stalks with bright orange caps; this mushroom sure likes to make a statement. Even moreso once you notice how it's shaped-a single stalk with branches upon branches emerging from it.
As with most other mushrooms, this variety can be grown via the usual methods into a giant mushroom when placed in a 2x2 pattern. Be wary; Dutch Caps grow even higher than Grandma's Shoes'-an astounding 17 blocks high, challenging the tallest trees of the Erebus (Eucalyptus, Baobab and Mahogany) for the tallest bit of flora (or fungus) in the entire Erebus!
Ah yes, the infamous Glowshroom. Veteran Erebus adventurers remember the plight that staying in a Fungal Forest for too long brings about; Glowshroomageddon. These roof-growing 'shrooms start as a single stalk block, but swiftly grow more and more stalk blocks with Glowshrooms on top.
How does this make them infamous? Currently, there's no limit to a Glowshroom stalk's growth, making them grow from roof to floor and everywhere in between. It is not advisable to stay in a Fungal Forest area you value too long without removing the Glowshroom stalks.
On the plus side, if you can reach them, Glowshrooms can be combined with a Torch or Glowing Gem to create a Glowshroom that's placeable as a decorative light source.
By far the rarest mushroom in the Erebus, these 'shrooms don't have a giant version and cannot be grown. The only way to acquire a Terpsishroom is through a rare drop by a Zombie Ant.
They are a critical ingredient in crafting Bryuf's Brew, the best Smoothie in the Erebus.