Skulk gives a running bonus to Rogues and Rangers who train in the skill. When they enter any room, they are automatically gauging its light versus shadows,
its areas to slip into some secret space, sensing the smells, etc. for increased availability to hiding. This in turn grants them a +2 per rank to HIDING, SNEAKING and will grant a +1 Bonus per rank to AS when Ambushing while Skulked. Up to +5 AS Bonus, +10 to Hiding related skills.

Ambush Mastery becomes available for those who've Mastered Skulk and Shadow Mastery. This gives a -1 to RT when Ambushing as well as +5 to DS when ambushing per rank. This is a running bonus up to 2 ranks.