If you want Elite Orbs of Alchemy, my suggestion is to farm the missions "5-2: The Sovereign Slime" and/or "6-2: Built to Destroy!" on Elite until you can get enough Elite Orbs. They have a low chance of dropping from treasure boxes, so you'll be at it for a bit of a while.

Even if you don't manage to get any whatsoever, you can still save the crowns you get from clearing the mission(s), as well as buy & then sell certain token rewards that you get from Brinks (i.e., pieces of the Brute Jelly set, the Pulsar, the Catalyzer, and/or the Static Capacitor) in order to build up enough crowns for you to buy unbound Elite Orbs of Alchemy from the Auction House, or use your newly-acquired wealth to buy Crystal Energy in the Energy market, then buy the standard 3-packs of Elite Orbs from the Supply Depot.

I'm sure others will have tips & strategies for doing this, but as for me, that's about all I can advise that you do.

They hardly ever show up in stratum 5 (mostly eternal). Only other stratum they show up in is 4. I dont get why they made only shining fire crystals in stratum 5 but not only elite orbs in stratum 5, wouldnt that make sense?

I think this belongs in the 'new recruits' section.

But anyway, ignoring where they drop (already answered), because the drop rate is so low (this too), the easiest way to get them is to save up, exchange crowns for energy, and buy the orbs from the supply depot with your energy. Normally the auction house rates are higher than the supply depot rates per orb. I'm assuming this is because every single orb that was ever in the auction house was bought from the supply depot, and people like to make money by charging more than the original cost on the orbs.

So, basically what corinth said.

For future reference, rarities such as Elite Orbs are discussed in the wiki page "Rarity".

To learn more, try using a web search engine (not the forum's built-in search) to search for threads. For example, Google "elite orb site:forums.spiralknights.com". You will find at least 10 threads.

Thanks. Sometimes people interpret my "how to search" posts as sarcastic. But they are actually intended to help.

Yeah I like Sewer Stash because it has a relatively high payout and arsenal stations every floor if you're heating.