Today, the official Borderlands account tweeted:

11 years of Borderlands 2 calls for 𝟏𝟏 𝐆𝐎𝐋𝐃𝐄𝐍 𝐊𝐄𝐘𝐒. This code also grants the 𝐕𝐨𝐥𝐜𝐚𝐧𝐨 weapon to add to your arsenal. Happy Anniversary, Vault Hunters!

🔑 CTWTB-X9ZHB-XBXT9-B3JTJ-3JKW6 🔑

Redeem in-game or at http://shift.gearbox.com! Code expires Oct 31

And they also tweeted:

This weapon is coming in hot!! Grab the 𝐕𝐨𝐥𝐜𝐚𝐧𝐨 if you haven't already!

🔥 CTWTB-X9ZHB-XBXT9-B3JTJ-3JKW6 🔥

Redeem this max-level weapon in-game for Borderlands 2 or at http://shift.gearbox.com! Code expires Oct 31

Part of the "Month of Mayhem". These guns are said to redeem at the max level for the game. Remember to redeem the code for each platform, if you play on multiple platforms.

Extra goodies (11 Golden Keys) because today is the 11th anniversary of the release of Borderlands 2.

Note that the "second" code IS THE SAME CODE - one code does it all, they just made two tweets, one highlighting the keys and another highlighting the Volcano.

As always, see the pinned post in this subreddit for the other SHiFT codes being distributed this month.