Yes so,, very simple,,

An item that works like a jelly and/or canopic jar- but for Battle beetles! It freezes them, rendering them un-trainable, they no longer age, no longer loose hunger- but you can still Trade them n such!

I find myself kinda,, shifting away from battle beetles simply due to their short lifespan, you barely get to do much w/them :(! But i'm sure an item like this would probably incentivize some people to collect and/or actually invest in beetle skins for their lovely boys!

It probably wouldn't be much,, about 1-2 maybe?? In the Oasis! Or even 3 if we're REALLY stretching it! Or, It could also come as a very rare prize for winning a beetle battle!
Ergo, perhaps pushing some beetle enthusiasts to use the battle feature more :0

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So basically just,,,

Primordial Nectar: " This strange liquid is sweet and tangy- feeding it to your beetles will make them immortal! "