Feats in Underrail are similar to perks or traits in other RPGs. They are permament elaborations of your character and serve the purpose to further customize your character build with unique active abilities, skill boosts or passive abilities. Feats do not boost Base Abilities, but characters gain a base ability point every fourth level.
For every even level in Underrail, you must pick a feat. New characters start with two feats. Base ability and skill requirements of feats check your unmodified base/skill scores, not effective scores that include bonuses.
In order to finalize your level up phase or complete character creation, you must spend all feat points. You cannot save feat points and use them later and you cannot remove or respec feat points once level up phase has been finalized.
Some feats cannot be picked when leveling up, instead they require training or other means of acquiring. One such feat is Psi Empathy. These were marked with (requires training) on the feat list before training them, or (Trained) once trained.
Veteran feats and specialization
Characters that have leveled past level 25 become a veteran. In addition to regular feats, veteran characters can pick feats from new veteran feat pool. These feats are marked with (Veteran). Veteran feats, at least in Underrail: Expedition, tend to be more general in nature, but they can also give your character some important bonuses that you cannot otherwise obtain. First examples of veteran feats were showcased in Dev Log #48: Veteran Levels.
Veteran characters also get 3 specialization points each veteran level, up to total 15 specialization points at level 30. These specialization points are used to further improve normal feats, often across a specific dimension. Your investment of points in any given specialization cannot exceed your veteran level (or the maximum allowed points for that specialization). Like veteran feats, specializations will not be available nor visible to non-veteran characters. For more details, see Dev Log #54: Specialization and Veteran Level Changes.