The act of First grabbing him is probably a little more shocking to Finbar than the fact that a large demon-creature just popped out of the ground. Given the alternative, however, he'd rather a moment of discomfort to a giant monster crushing him.
As First drags the wincing Finbar out of the way, the Fyarl crashes onto the ground on all fours and roars something in Abyssal. As One closes in, the Fyarl will fire a stream of mucus at him. If he's not quick enough, it'll dry and harden upon contact. It's a defense mechanism meant to immobilize victims before consumption. Regardless of how the situation with One turns out, the demon will not be able to recover from the mucus expulsion fast enough to effectively counterattack Alpha. Fortunately, the creature is very stout and it may be difficult for Alpha to actually tackle. It is not an impossible task, but it will surely be quite difficult.