Erik will absolutely interfere, if only because the creature is attacking Tadhg rather than the reverse. None of them (presumably) have any idea what this thing is capable of doing, after all, apart from the usual things one may do with a mouth so hideous, with clawed limbs worthy of a Jabberwocky's envy.
(Is there a Jabberwocky in Baedal? There'd better not be.)

A guttural sound of effort announces his involvement, which comes in the form of eight or nine steel railroad spikes, airborne with the intent to intercept the beast's hideous body mid-leap. Each spike is about eight inches long, sharpened nearly to the point of unfairness, and notched once each to make removal more difficult—never mind what he may yet do to their shapes should they become lodged in the aberration's flesh.

There are more of these in the truck bed, too, awaiting their turn. He came well equipped this time.