Two Romulan Z-Series Prototypes

These two Heavy Warships were developed in the 2280s, and it was unclear, even to Starfleet Intelligence as to whether or not they were actually under construction, and so they were kept to the Threat Files for well over a Decade, although in 2291, it was finally discovered that due to the Star Empire's poor resources, only one Z-19 and one Z-20 were completed, the Z-19 in 2292, and the Z-20 in 2298, both ships used in careful, stabbing assaults on some Federation and Klingon bases, sometimes assisting the IKS, and the Z-20 always being escorted by two T-12 Bravewinds and four T-5 Fire Swarms, all seven ships destroyed in an attack on an Andromedan Base soon before Operation Unity in 2302, soon destroying the Base, a Dominator and two satellite ships, making way for the combined Milky Way Forces, and the Z-19 was destroyed in a battle against the USS Proxima in 2311.