Non-Shifters
Most shadowlings are Non-shifters, they have 1 form can can never change it. The can not walk the Pattern or the Logrus, nor can they inscribe one. This is the vast majority of shadowlings.

Limited Shifters
Some shadowlings have a limited number of alternate forms that they can take in addition to their base form. Circumstances for the change vary widely from freely able to change to limited in time and place (like werewolves can only change on the full moon, and then have to change).

• Alternate Form
  1 point
  The creature can have one additional form (either another shape, or something like invisibility). The creature must maintain the same mass. Examples are werewolves.
• Named and Numbered Forms
  2 points
  The creatures has up to 12 additional forms, including ones of different mass (up to 50% either direction from the base form). Examples include a vampire than can change into a wolf, a large bat, and a handsome prince.
• Limited Shape Shifting
  4 points
  The creature has many forms and can learn more (12 starting, 1pt/each for additional forms), it can change parts of its body rather than the whole. It can accomplish mass changes with less than 100% change from the original. It can not change states of matter, aura or persona. The creature does not heal when it changes. Examples include a mimic that once it touches a creature can imitate its shape.

True Shape shifters
Before the creation of the Pattern and the Logrus the creatures living around the Abyss were true shape shifters. They were unlimited in form changing freely when they desired or it was needed.

The inscription of the Logrus made this more difficult, yielding two types Common Shape shifting which is also known as Pattern Influenced Shape shifting (even though it didn't exist yet) and Skilled Shape shifting.

With the added powers of the Logrus few learned Skilled Shape shifting. With the inscription of the Pattern, everyone in the region influenced by it was bumped down a level. Common Shifters lost their ability entirely, Skilled Shifters could only do Common Shifting. The Pattern seemed to have to effect on the Limited Shape shifters so the lines of Chaos began to mingle with them in an attempt to regain their powers, particularly with shadowlings possessing Named and Numbered. A few strong individuals retained or learned the abilities of Common Shape shifting though it was difficult to do and to maintain these forms.

Those with Blood of Pattern being True Shape Shifters could learn Common Shape Shifting, though few did believing their form to be static since if it was not learned before walking the Pattern the subconscious imprinted a static form upon them. Even fewer learned Orderly Shape shifting, a power of the Pattern in their blood that had to be activated by walking the Pattern.

At least one line of this family, its ancestry lost in antiquity, also mingled with limited Shifters, gaining the Alternate Form: Rebman Form. Once again if not learned before walking the Pattern it is locked out.

As the eons progressed the lines of chaos became throughly infused with the Blood of Limited Shape Shifters, giving almost everyone a number of forms in any environment. They also discovered that parts of the Beyond had drifted away from the Pattern influenced areas and True Skilled Shape Shifting could once again be used.

This we have the examples used in the books:

In the First Series
• Oberon changes appearance and persona to Ganelon but retains his strength. An example of Orderly Shape shifting.
• Dara seemingly randomly shape shifts under the stress of walking the pattern. She assumes Demon form, that of an enormous cat, a faceless woman, an angel, and a tower of ashes. An example of her Limited Shifter Heritage. The tower of Ash was not a change in state of matter, it just appeared as ash from the outside.

In the Prequels
• Oberon changes his features to mimic others several times. Using Common Shape shifting.
• Oberon grows and extended arm inside his body during combat. This takes a lot of effort and he can only defend while doing so. Using Common Shape shifting
• Oberon's opponent in the same combat assumes Demon form just before fighting. Using Common Shape shifting
• Several individuals are described with non-human appearance as "standard" obviously shape shifting is not very prevalent or they would change it. Showing the failure of most in Chaos to learn even Common shifting due to the influence of the Pattern.