Add these onto the Parent Race
Ability Scores
Int +1
Expert Tunneler
As a Pitstalker, you are naturally suited to digging. You gain a burrow speed of 5. The holes you normally dig are about three feet in diameter. Burrowing through solid rock or most buildings instead takes 10 minutes per 5 feet and requires a pickaxe or similar tool.
Naturally Stealthy
Kobolds often try to hide behind their larger allies for survival. You can attempt to hide even when you are obscured only by a creature that is at least one size larger than you.
Trapcrafting
You have advantage on rolls made to detect, create, or disarm traps. In addition, when a trap you have built is activated, add +3 to the DC of any saving throw to avoid or resist its effects.