The Mori Mori no Mi is a Paramecia-type Devil Fruit that allows the user to create and control wood, this ability makes the person a Wood Human (木材人間 Mokuzai Ningen). It was eaten by .
The Mera Mera no Mi is shaped like a bunch of bananas with various swirls on it. Brownish of color with a darker brown stem holding the individual sections together.
The user is able to create wood that ranges in thickness and sizes. He can give it shape and form it as he wishes allowing him to use it for anything from defense to attack or just for repair of many different things. He can make very strong wood if he wants to making it hard to break, even for some Devil Fruit users making it very efficient in use but it does take longer to make then weaker types of wood when a large amount is made. The user can create large walls to get away from enemy's. The user can also cover his wood in Busoshoku Haki which can make it stronger then most materials, even swords or attacks.
The user is able to create many complex things like ships and more. The fruit also allows the user to create platforms across islands and on the ocean, allowing the user to get over body's of water. The fruit also allows the user to create himself armor that can he can fully move in by using his power.
The Devil Fruit is believed to be able to even make the Adam tree wood which can withstand cannonballs and gun fire quite easily. It is know for being the strongest wood in One Piece, this wood was only used on the Oro Jackson and the Thousand Sunny making it very rare.
The user is affected by the standard Devil Fruit weaknesses and Sea Prism Stone. Some types of wood created can be set on fire or even cut if they are thin enough which can waste time. The stronger woods take longer to make when in large amounts but the user can speed it up but it will cost him in stamina and drain him. Wood is merely a blunt object when used in combat compared to swords, knives, and guns when not shaped.
The user can have a hard time against Devil Fruit users like the Mera Mera no Mi but can still beat them using a fire proof wood as even normal wood cant get incinerated, instead it gets set on fire but still can be used. Another fruit that could be strong against this fruit is the Magu Magu no Mi which can likely burn through wood. The Devil Fruit likely has a number of fruits that could go against it.