Favored by the Fianna, Stag is a primordial and ancient totem of nature and virility, as well as Master of the Wild Hunt. Stag occasionally comes to the aid of lost Garou or Garou in dire straits. Those Garou who follow Stag gain the abilities to survive in the wilds and an affinity with nature. While almost all Garou (save for some urrah Garou) respect a Stag pack's affinity with nature and the Wyld, the Fianna especially respect those who follow Stag and often accommodate them with wine, lodging, and... other favors. Fae are far less likely to do mischief or harm towards those who pack under Stag, unless the pack commits some offense.
Packmembers are not only able to survive in the wilderness, they thrive; they never get lost if they are in the wilderness, and will instinctively know which direction to go in to find the best available food, water, and shelter.
Whenever a follower of Stag leads a hunt, it's much more likely to go off well (+1 to all tracking rolls).
If they are in particular trouble, there is a chance that a white stag will appear to help them to the best path out, or to the best solution to their problems. Of course, a white stag may also be a harbinger of trouble, as well... (GM call; it won't be clear which is going on, for some time.)
Packmembers have double the chances of impregnating or becoming pregnant (whichever is relevant) with double the odds of producing Garou offspring.
Stag's followers must always aid, if possible, Faeries or Fianna who are seriously injured, seriously threatened, or in a life-or-death situation. Wild animals may well appear to urgently inform them of these issues. If they do not attempt to aid the Fae or Fianna in question, they will immediately forget where they are, and will lose all native sense of direction until they either perform Contrition, or save the individual in question.
Stag's followers must observe the Celtic holidays, and properly propitiate the Fae during them. (This does not guarantee the Fae's favor, of course...)