I did it to illustrate my specie Niyassur (ニヤスル - Niyasuru.

Sorry the errors, I used the translator to write it. :[

Niya's tail is the strongest part of body. Male niyas can get up to 3x their own weight using the tail while females 1x their own weight. Niyas use tails for various things, such as carrying their pups, climbing trees, balancing, picking up light and heavy objects, using them to swim (just as crocodiles use their tails), warming up, defending themselves, and many other things.
There are 6 types of tail that a Niya can have. The Niya even having two or three tails can not have them different, all will be of the same type of brush on the tip. The types of tail are:

Type 1 - Normally (Common): It is the most common type of tail that a Niya can have being present in both males and females. Its bad point is certain slowness to complete most of the designs.

Type 2 - Fluffed (Uncommon): It is a tail only present among females. The hair is much softer and softer than the other tails. Its bad point is often to blur or undo some types of magic by being difficult to use it for attacks. It is considered the best to draw charms such as Recover and Blackout.

Type 3 - Needle (Rare): It is a rare type of tail. Their hairs resemble small needles, they are difficult to draw, so the Niya who carries this type of brush will have some difficulty in drawing, but in return, his tail can be used as a spear (needles) at enemies.

Type 4 - Duster (Super Rare): It is the rarest type of tail to find. The Niya that carries this type of tail will almost double the triple damage when using enchantments that involve inkcinese, however due to the size of the edges of the brush some types of magic can not be done (Viel of Mist, Recover, Inferno, Deluge and Trap Box).

Type 5 - Slender (Unusual): Considered the best brush to make drawings. It is a simple and quick tail, hardly any difficulty to make normal drawings and drawings involving inkcinese.
Type 6 - Small (Unusual): Used for more detailed drawings. It is the smallest of all tails. The Niya carrying this type of tail will cause half the damage of a normal brush when using tintacinese, but will have speed almost triplicate when making drawings.

Without its tail the Niyas can die quickly by losing much of their ability to use magic, fortunately their tail if it is torn off may grow again. In males the process of regeneration lasts on average some weeks due to its curing factor whereas in females the process lasts a few months to years.