[@Digizel] Rather than use your critical success to Aid, I'll allow you the opportunity to roll a separate Aid action roll with a flat DC of 15 to see if Saur can Aid Thornharp in her own stealth roll! Saur was so ready to hide that he can take the opportunity to try to help one other person to hide as well. 

Now it's your turn to describe how Saur would  Aid Thornharp to hide, and roll against that DC!