I've seen a few threads on the net about this and the general consensus seems to be that the egg-bearer can use the egg in a challenge, whether it be in the 1st, 2nd, 3d, etc. round of the challenge. This is based on the FAQ of impact hits/breath weapons/stomps/thunderstomps which function similarly, which says that they can and must be used in a chellenge only against the challenger. However, consider 2 possibly problematic situations: 1) What if the egg-bearer is fighting a mounted challenger, whose mount is a monster or some other creature that can be wounded separately. Do the egg's attacks get distributed like shooting (i.e. 1-4 on the mount, 5-6 on the rider) or do you choose where all of them go? Cos it doesnt say in the egg's text. 2) Say my Scar-vet (who's in a unit of TG with a Slann) is in a challenge with an Orc Warboss (who's in a unit of Savages). The Slann, not the Scar-vet, has the egg. Can the Slann use the egg against the Warboss while he's in a challenge with the Scar-vet? The obvious answer here I think is no, solely because the egg says you direct the attacks against the "unit" not a "model". . . . BUT, would your answer be different if my TG + Slann/egg + Scar-vet unit was in combat with a sole Orc Warboss on a Wyvern? In that case, the Warboss IS the whole unit, and p.102 BRB says "These two characters [i.e. the ones in the challenge] must direct all of their attacks against each other — they cannot be attacked by any other model for that round of close combat." Emphasis on "attacked". No other models from either unit may direct an attack against the challenge participants, but can they use magic items against them? Fluff-wise I would be inclined to say no, as the whole point of the challenge is that the two are kind of being "cheered on" by the other troops and nobody wants to interfere, but hey, who's to say a sneaky mage might not cast a quick hex (or maybe an enchanted egg!) into the fight? Not everyone fights with honour. This is supported rules-wise by the fact that the whole reason the egg (arguably) can be used in a challenge by the challenger is the FAQ on impact hits/breath weapons etc., and if a third unit (say an angry Stegadon) charges the Wyvern Warboss while he's in a challenge with the Scar-vet, surely he would do impact hits - so why couldnt a third party to the challenge similarly use the egg?