Kristina had no idea what was so special about the herb Luna just mentioned and neither did Uriel or Nika, which is why she was shocked to see their moods shifting in an instant and getting ready for combat despite them being supposedly in the clear. To them, the fact that Luna mentioned the name of a herb was already reason enough to raise concern, but her letting out an 'uh-oh' was the ultimate danger sign.
Nika pointed her gun at everywhere and nowhere in particular ready to open fire at the slightest movement while Uriel kept the Red thread of fate on one hand and the Magnum revolver on the other, mentally prepared to activate Dash to react to whatever danger Luna had just warned them about.
The entire place was mute as though someone had switched off the sounds of nature, a hint that something was going on, yet it took them almost a minute to notice that there were no trees in sight neither of the trail they just followed.