Experience gain & levels
As with any system that has a level or progress, the player would like to know how they are progressing, how to measure how well they are doing, for themselves and in comparison, to others. Within a narrative, the seven saviors would (hopefully) simply know that through their experiences and activities they have become better individuals. But the player will most likely want something that illustrates this experience, as in Fence Builder Level 1, after completing fence reinforcement challenge for the village, the player is now a Fence Builder Level 2.
Having experience gain and levels as a visual indicator is the primary, and easiest, form of feedback for mastery focused players. Specifically, because it records how well they are doing and how good they are becoming at something, even though it is an arbitrary representation of learning they will have hopefully have internalized. Its particular usage in measuring progress is to indicate the level of mastery versus the level difficulty the player can handle. A gradual increase in difficulty coupled with a visual representation of progress helps you as the designer to adequately create corresponding challenges, but also psychologically aids the player in believing they are ready for the challenge.
This rising angle of difficulty versus ability automatically engages the player in both the experience and the story. The added benefit of the visual indicator is that if the player progresses too quickly and is unable to handle the new challenge just yet, they at least do not become alienated, as the visual leveling process does clearly show that they should be able to do it. This should motivate to keep trying until they succeed.
The boss fight should be the pinnacle test of a line of progression for a player. Boss fights can be seen as narrative events for your player base, as with our seven-savior example, the boss fight is when the bandits finally attack the village and the seven players must use all of their gathered experience, knowledge and preparation to defend the village and defeat the bandits. Narratively you can go one step further and have a final single boss engage them. In a traditional game, this would more than likely occur.
The boss fight events should be enough of a challenge that the players require a combination of several skills to defeat the “enemy”. The should struggle to win, with failure being a constant consequence. But when they do eventually win it should offer a sense of epic-ness and the achievement should warrant the effort invested. The worst outcome of a win or loss is if the player feels cheated or that it was a fluke in some way. With a win, it can be forgotten but with a loss, this feeling can often be compounded. So be careful in how you balance the difficulty versus the ability of your players. The best advice for this is gradual playtesting of all previous challenges and accordingly setting the final challenge in accordance with the data gathered from those tests.
The added benefit of the boss fight is that going forward in the experience, a previous boss can become a standard and continuing challenge for the players. If they have reached a high enough level or have entered an end-game phase, then using previous “bosses” as it were for continuing challenges, allows them to refine their skills and knowledge. This is a good method for keeping experienced players engaged and allows the continued practice to keep everything fresh in their minds.