Grehha and Raaha walked through a narrow channel whose entry was restricted. Every second, Grehha could feel powerful waves of Internal Inertial Gravity washing over him, barely managing to avoid harming him.
He wasn't part of the 1st Empyrean Tusk's immune system. Hence, the latter's immune response was instinctively trying to get rid of it. The Empyrean Tusk diverted part of its attention to avoid killing Grehha.
Thankfully, they intended to keep their visit short. So, the 1st Empyrean Tusk wouldn't experience a rash. The deeper into its bodies a foreigner went, the stronger the Empyrean Tusk's immune response.
When it was an enemy, the Empyrean Tusk could simply focus on killing them. But when it was a Mammoth Clansman, it had to exercise caution to avoid harming them, which stressed it gradually until a rash broke out.