A tribal group that the party wants something from (eg. horses, specialised bows, arcana) will only deal "Fingers of the Fist". Ie, at least one member of the party must successfully prove themselves as a tribal warrior for which there is a traditional initiation. The traditional fighting band is the five strong "Fist", consisting of "fingers" (initiated warriors) and led by a "thumb" - the eldest finger.
Normally tribesmen would go through initiation at 14-16 years old, so the procedure shouldn't be too dangerous but they may embellish the procedure somewhat for outsiders. This can be used as to make use of some less frequently used stats, eg. a rough ride to test horsemanship. A test of pain endurance should be part of it. Tattooing or branding are obvious and could use things like max-hit-points, constitution, mental stamina, stats for the test. A test concealed to the players could be made by an estimate of the no. of times the character has been wounded. While having limited playing interest, the resulting brand might led to interesting plot developments "back home". A more interesting component of the test could be a stealing mission: a central totem of some kind in the tribal villages is generally surrounded by curious pottery votive bowls. The design of these bowls being distinctive to each village. The task is sneak into a neighbouring village and pinch a bowl. Since the tribes live pretty much at peace, spilling of blood much more than a bloody nose would be severely frowned on and likely to cause blood feud. (The party may or may not be told this depending on how you might like to develop this). This is naturally a game played by the younger tribes people and the night guard on the totems would only be 13-14, on possibly a new "finger". Their preferred "weapon" against would-be raiders is a foul yellow dye that takes a week or so to wear off. A person marked with such a dye, would be a general laughing stock. A daylight raid would be considered very daring though no especial guard is placed on the totem at day and entry to the village could be gained on some other pretext.
The test should conclude with combat. Suggested is tackling a suitable large predator - but with no armour etc., and only a dagger for a weapon.
An enemy (may be a monster as well as human) killed in honourable combat (ie the enemy had a chance), may qualify the "finger" for a silver ring awarded by a war council of "thumbs". An extension of the plot here might be an incident that lets the players become Ringed Fingers.