Whoever uses the pen can bring anything they draw, usually anime characters, to life. The more skilled the artist, the more powerful the creations they can make. Axol, being the most skilled with Inkweaver and artistry in general, is the only character shown to be able to wield it to its full potential. However, they tend to only last for a few minutes and are lacking in intelligence.
When Inkweaver uses Inkling ink, the characters become stronger, smarter and they last longer. However, they will still disappear after a set amount of time, unlike Saiko Bichitaru who can last indefinitely. (Due to the fact that she was created by Kamek's Wand instead of Inkweaver).
Despite being made of ink, the ink characters do not dissolve in water, as Godzilla can attack anyone approaching the island, however this could be contradicted by his colossal size.
As an ink pen, Inkweaver will only work so long as it has ink supplied to it. More powerful creations also seem to require a larger amount of ink to bring to life.
However, the Inkweaver needs professional use for its creations to be able to function properly. Poor drawing skills will mean the creations will die quick or not being able to function properly no matter what ink it came from.