Plaguebringer's Skull

All three pieces go in the social slots and do nothing for your defense. Making them still takes progress, though. The recipe wants Bones, so Skeletron has to be dead, and the rest of the materials only grow in the Crimson. That puts it in a small group of contest sets you cannot throw together on day one, alongside its Corruption opposite, the Timeless Traveler's set.

A Corruption world does not lock you out. Reach Hardmode, build a graveyard, and the Dryad will sell Crimson Seeds while she is standing in one. Plant them somewhere isolated, let the spread do the work, and every material you need grows in your own world. Fence the patch off with a wide gap of inert blocks first unless you want it eating the rest of the map.

Wearing the full set lights you up with cursed flames trailing off the cloak. The color follows whatever dye you put on the cloak specifically, not the helmet or the boots, so one bottle changes the entire effect. Two players in the same outfit can look completely different for the price of a single dye.

The tooltips point at Destiny 2. Ahamkara are the wish granting dragons in that game, and the Drifter, one of its vendors, ends half his lines with the word trust. The cloak's line about a blight weaving world ender is aimed at Riven in particular. The original design came in as a player submission during the Journey's End vanity contest.