"Umm...oh, yep, yep! This box...is an EVIL box! That destroys other boxes!" 

The sneevils gasp. 

"Box... destroys uvver boxes?!" 

      "Das bad."

"Das very very bad."

     "What's da ebil box look liek?" 

Elan remembers this one!

"It's black! And gold. And has a picture of a dragon head."

"Black an' gold wif dragon hed..." 

The two sneevils look at each other. 

      "Has you seed a box liek dat?"

"No. Has you?" 

      "Nuh-uh." 

One of them runs inside the tree and up through the interior, shouting as they go. "BAD BOX! We gotta find da EBIL BLACK BOX and get it outta heer!"

"Thanks for your help," Elan tells the guard who stayed behind.

These guys seem pretty nice, honestly. Or at least not too hard to deal with! It might be because he's talking to them one-on-one and has smaller demands (in a way) than "stop stealing all our stuff," but it still makes him hope that there's some way of dealing fairly with sneevils without getting boxes and other stuff stolen.

Oh, it's easy to get sneevils not to steal from you! You just have to not have any boxes for them to steal. (Is what the sneevils might say if he asked them.) 

Twilly's lie about the "evil box" seems to have really stirred up the ants' nest. Sneevils are shouting up in the branches, running along rope bridges to neighbouring trees, and generally raising a ruckus all over the tree fort. 

Eventually, the guard returns with some friends, each of them carrying a box which...sort of matches the description? One is black with a big gold lock on it but no dragon symbol, one is unpainted wood with a dragon symbol painted on it in white, and one has a gold lock in the shape of a dragon's head. 

"Iz any of deez teh evil box?" 

Elan… thinks that maybe it's the last one? He points at it.

"Can we take a look at that one?"

The sneevil carrying box #3 sets it on the ground so Elan and Twilly can get a better look at it. 

Twilly doesn't even need a full second before his ears droop. "Nope, not this one. Our box—I means, the evil box—was black, and this one is brown. Elan, I doesn't think the box we's looking for is here."