Recently, we have held a few vanilla Descent quests with all of the expansions added in, including TOI. Several of the quests involved Monster Egg props within the dungeons. In the particular quest we were in, the eggs had an armor of 4 and a health of 4.

The overlord took the position that since the Eggs were props, and not enemies (and/or monsters) to be targeted, the heroes could not use any of their feat cards, and could not use any special ability and/or skill that would require targeting enemies and/or monsters. So, for the most part, the heroes had to rely on whatever weapon they had to attempt to pierce the armor, and reduce the health to 0.

The question I have for those that either have played quests with Monster Eggs, or who just have an opinion to offer, is:

Are Monster Eggs considered enemies and/or monsters?

I believe most skills and feats use language like "when making a ranged attack" and do not specify anything about the target of the attack, so it may actually be significant when a card specifies "against a monster" or similar. I think it's reasonable to conclude that skills like Cleaving would not trigger after destroying an egg prop, but skills like Quick Casting could definitely be used.

... why would you /want/ to waste a Feat card on the monster eggs? 4/4 should be done away with in one hit, sans feat cards. If I were the OL, I'd allow it gladly

-shnar

From the Tomb of Ice rulebook, page 6 (emphasis added):

"Monster eggs can be attacked as if they were normal monsters , using the wound and armor values described in the quest."

It sounds like you're probably playing a fan-made quest, in which case you'll need to read the quest rules carefully and see if they change anything, but the default rules appear to allow them to be attacked in any way that a monster could be attacked.

Also note that eggs do NOT block line-of-sight, so you could attack something behind them, or center a Blast attack on the far side of an egg.