Each weapon references one of Kabam’s Developers or Gamemasters who were working on the game at that time:
Sunshine Shiv: designed for SGT_Sunshine, a GM.
Robobow: designed for NullBot, a GM.
KoalaPOW: designed for KoalaP, a GM.
Spicy Wand of Spice: designed for SirRacha, a GM (whose name is a pun on sriracha, a type of hot sauce).
Doctor Swordsworth: designed for DrBearsworth, a Dev.
Arbiter’s Wrath: designed for ArbiterZ, a GM.
The weapons are soulbound.
Initially the item drop rates were relatively generous however at some point they were lowered making these weapons currently very difficult to obtain, being rare loot in a very rare-to-see dungeon.
Battle for the Nexus keys have made occasional appearances in mystery boxes, and as event loot over the years.