The Scroll of the Purple Crayon, at first glance, appears to be a regular roll of parchment.

When the scroll is opened, a purple crayon falls out and the scroll unrolls to 1 ft in length. There is nothing written upon it.

The user must use the purple crayon to draw what they desire. There are no limits to what can be summoned. The user must roll 1d20 with their performance bonus to decide the quality of the drawing. The higher the roll the higher chance of getting what you desire. If you critically fail the desired summon appears with 1 hit point and weakness to everything. They appear see-through but outlined with purple. 

Alternatively, the Game Master can decide the user must draw what they desire Outside of Character. The Game Master then decides if the drawing is sufficient enough to bring in the desired summon.

The Scroll of the Purple Crayon is a one use item, unless a wish spell reverts it. 

The user may not summon that which does not exist.