In writing about Rime Tower over at my other blog, I realized something that might make tier definitions easier to cement in peoples’ minds.
Consider a difficult living environment — arctic taiga, Saharan desert, Amazon jungle, and so on. For those with strong associations to those environments (that is, talents), you might see the following characteristics.
Basic: the person can survive there. It might be a fair bit of work, but he knows the materials, tools, and techniques needed to not die. Almost always. In the taiga he can reliably find enough food to stay alive, find sufficient shelter, and so on.
Expert: the person can survive there fairly easily. He may still be impeded by the environment (traveling in snow, across the desert, or through jungle is still slower than plains) but they can be more or less comfortable doing so. He knows the tricks for getting around in the snow such that while it is still slower than walking across grassland it is not particularly arduous.
Heroic: the person is no longer particularly impeded by the environment and considers it as most people would consider plains or easy hills. He can get around at normal kinds of speed, sure-footed enough that ice isn’t an issue, and so on. He can’t see through a blizzard, but can tell by disturbed snowfall that something is present, and has become sufficiently adapted to sun reflecting off snow that he is not bothered by snowblindness, even without eye protection.
Master: the person actually starts to draw specific advantage. In the ice fields he is not only not impeded by the conditions (as foreigners might be), he can start to call on the power inherent in the place — call up freezing winds, become one with the snow and hide, and so on.
Champion: the person starts to embody the environment. His body radiates cold, his skin pales (even to pale blue), the wind and snow pass through him without hindrance or discomfort. Even more than call on the freezing wind he can become one with it and travel on it.
Legendary: I’m not sure yet how to exceed what Champion does here. Perhaps he becomes a part of the environment — not just embody the power of it, but actually join with it in some manner.
Not all talents will work quite this way, but I think the above might provide some guidance for the sort of range and nature of the abilities that might be gained from some of them. Low tiers focus on the mundane, higher tiers become more fantastic.