While you are making preparations, Zaron follows you to the top of the cave and says, "Let me make sure I have give you all the instructions and information I have before you go in."
He opens the top of the barrel and points in. You see various rune inscribed jade-like stones. "These are wardstones, which disrupt the phase spider hatchlings ethereal jaunt ability. That will prevent them from jumping to the ethereal plane once you have caught them."
He also hands you a jar that has similar stones. "Each stone will affect a 10 foot diameter sphere. If you place them strategically in an area and lure in the hatchlings, you can prevent them from phasing out while you catch them and put them in the barrel. They are not smart, but smart enough to know that if their phasing is not working, they should move. You will only have a limited number of tries before they flee out of the area."
There are 8 stones in the jar.
"I also asked around to get information about the cave. No one knows much, but one rumor was strange enough that it stuck with me. One patron said there is a dragon in this cave that has been woken up by the ethereal jumps. Another said that it was actually just a giant phase spider that looks like a dragon and that it has been in hibernation for a long time. What struck me is that none of them denied that there is...SOMETHING...very big and dangerous in there. So be careful. I hate to admit this, but I have a paralyzing fear of spiders. That's the real reason I'm hesitant to follow you in, but I will do it if you get in trouble."
He hands you the jar
(determine who will take it or if you will separate out the wardstones) and then he says, "One thing I've also come to learn about the spiders is that the constant use of blinking causes an ethereal fog, which is not physically dangerous--at least, I don't think so--but it will create visibility issues. Oh, and these spiders like to phase out to the ethereal plane and then phase in right behind you and attack, and they do have poison, so be careful."