Aetherium armor is made from the new type of ore spawning in Overworld. The processing of Aetherium crystals into the ingots is when things get interesting. Prepare a cauldron filled with lava, toss the crystals in, and get yourself bars. The final twist is that Aetherium is not stable enough to make armor. Emerald armor would be the base for all crafts.
With Warden's armor set, you can see through walls. As you could've guessed from the name, the thing is made from parts of the Warden mob. The equipment of the complete set improves your night vision.
Phantom armor is another cool one. It is made of Phantom parts and bones. One item that excites me most is a whip.
Enable all Experimental gameplay features in Settings.
Reason: A new experimental weapon added - the Scythe