If you're looking to upgrade your weaponry to one of the most powerful in the game then you're going to need to know how to get the Buffalkor Crystal in Islands aka Skyblock! Where to get it isn't really a problem, however, it might take a while to actually obtain one.
Buffalkor Crystal Guide
To get a Buffalkor Crystal, you will need to kill Buffalkors and get one to drop it as loot. This is an extremely rare drop, so you might be after it for a while. I'm going to quickly run down what you should do to make this a bit easier if you really want to upgrade to the highest tier of weapon at the moment.
Before bothering with this I would try to get yourself the Iron War Axe. This is an upgrade to the Wooden Sword which is super weak and takes forever to use against a Buffalkor. You need 3 Crystallized Iron, 1 Steel Rod, and 40 Iron to craft it. A Steel Rod and a bunch of Iron isn't too difficult, although it can be time consuming if you don't have an auto-miner or totems setup. The Crystallized Iron is a bit of a pain, because you need to mine iron nodes to get it. It's similar to the crystal because it's a random drop and it's rare. So, try to mine a ton of iron and hope you get one sooner rather than later. You might be able to trade for some if you watch chat.
Roblox Islands Coverage
Once you've got your Iron War Axe, you can then go to Slime Island by purchasing a Slime Island Key. When you are there you will need to kill a bunch of Slime for a random chance to get a Buffalkor Key to drop. This drop rate isn't too bad, so you shouldn't have to do this for very long. Once you have the key, go through the Buffalkor portal to enter Buffalkor Island!
Now, you just need to slay Buffalkors over and over until the crystal drop. There's no real trick to this unfortunately, you just have to put in the effort if this is something you want to spend your time on! Make sure to bring some food because the Buffalkor hit pretty hard and you don't want to die!
Right now, you can only really craft one weapon with it, so it might not be worth bothering to get if you don't need to farm Slime or Buffalkor.
Gilded Steel Hammer
The Buffalkor Crystal is currently used to create the Gilded Steel Hammer, which is the strongest weapon in the game. You need 1 Buffalkor Crystal, 1 Gilded Steel Rod, and 40 Gold to craft it at an Anvil.