Taint comes in two forms, Corruption and Depravity. Both can take hold when one enters a tainted local, encounters a tainted creature, or interacts with a tainted item. One can have both Corruption and Depravity at the same time. Any and all effects of these conditions stack.
Taint can not be removed by any means other than by making the required constitution or wisdom checks to do so. However, if one spends a night in prayer and fasting you may replace the daily constitution or wisdom check with a Religion check (either your own, or that of one joins you in the vigil).