Protectors are the more visible half of the Guardsman duality. They are the ones who physically shift into canine forms, starting in adolescence, unlike Handlers, who do not shift. They exclusively take the form of "large" breeds, most commonly resembling German Shepherds, although depending on region/heritage they can more closely resemble breeds such as the Kunming Wolfdog, Tibetan Mastiff, Aïdi (Berber dog), Akita Inu (exclusively of Japanese descent), Siberian Husky, and Saluki. Breed resemblance is not exact, accounting for the nomadic and constantly shifting nature of human civilization. Certain very old Guardsman families are almost considered their own "breed" with particular characteristics that set them apart from both known dog breeds and other Protectors (e.g. the legendary Russian family, Dolgorukov, who tend to produce Protectors that resemble Russian Wolf Hounds). Likewise, Maori Protectors of New Zealand tend to shift into larger versions of the Telomian breed, which, like the Japanese manifesting as Akita Inu, is particular to their heritage.

Protectors are famously tragic figures, due mostly to the fact that they die when their Handler dies. A lot of mythology has built up around this phenomenon over the course of history, but the basic fact is that a Protector will experience fatal heart failure upon the death of their Handler. Research into bonding has identified this as a severe form of sudden-onset bond sickness. However, that has not stopped cultures throughout the ages from romanticizing the phenomenon and layering it with various mythologies as to explain why it happens.

As well, Protectors must bond by the end of their transition from childhood to adulthood. For most, this translates to about 25 years old at the latest. A Protector who remains unbonded past that biological marker will succumb to bond sickness and die. This rarely happens, unless a Protector is purposefully kept locked away or lives in a very isolated environment. The average age of bonding for Protectors is 18, although enough get to 23 or 24 years old before bonding that it is not particularly remarkable. There is only one documented case, from the 1930's in Chicago, where a Protector lived in good health to 29 years old before bonding (ref. Jecket Harper).

Guardsmen in general are hard to identify in childhood. Although there are several chemical markers that can be tested for, they are not exact and cannot accurately predict whether a Guardsman will manifest come adolescence (whether these markers can be construed as identifying "latent" potential is hotly debated within the ranks of the Institute, but denied publicly). Protectors are most easily identified when they start to shift sometime between the ages of 10 (earliest) or 13 (latest). If the family is unprepared for the possibility, this can be traumatic — a situation more often encountered in poorer communities/households. Even when the family is aware of the possibility and is looking for signs, the first full shift is often painful and confusing for the child.

Protectors occasionally bond with a Handler in tandem with another Protector. While this phenomenon is rare, it is not unheard of or unstudied. While these Guardsmen triads are technically as stable as any Guardsman pair, they have over the course of history been described variously and contradictorily as unstable, demonic, sacred, unnatural, divine, perverted, or as natural perfection.

For information about the role and status of Protectors in society, visit the Social Roles page.