Stealth Mode/Stealth Skill

Exactly what it says on the tin.

Toggle stealth mode, move slower and be less noticeable to hostiles via sight and sound.

The skill should probably only go up if you’re actively doing so within normal detection range of live hostile entities to avoid boring power-leveling via sneaking in a circle in the middle of a field far from enemies.

It’s on the list of things to be added.
Actually a range of movement modes including sneak(move quietly), crawl(low profile, harder to spot visually, also quiet), walk(default), run(move faster, make more noise, consume endurance), and possibly sprint(way more noise, much faster, and burn through endurance FAST).