List of Boss Conceptions

Medium

 * A.R.I.A and S.P.I.C.A (Atrocious Ruler of the Irregular Air and Super-Powerful Inhabitor of the Cursed Air)

Hard

 * Apopalypse Bloon

Only My Railgun

 * B.L.I.T.Z (Blimp of Literal Indestructibility from the Thermal Zone)

There Can Be Only One Part 2

 * A.E.B (Anti-Explosives Blimp)