Halcyon-class light cruiser (EXverse)

The Halcyon-class light cruiser was the lightest cruiser class in service with the UNSC Navy. Built by Reyes-McLees Shipyard to modernize the UNSC cruiser fleet, it lacked all the requirements needed to make the proper job, being undergunned and underpowered; the only point in favor was the impressive, but also expensive, hull structure, which was far more durable than any other ship ever constructed. However this structure drain considerably Navy's resources, in addition to other flaws, so another block without that complex structure was designed two years later, which improved its capabilities, however not that much useful to convince Naval Command not to cancel further orders.
The Halcyon-class was rarely used during the Insurrection because of aforementioned drawbacks, and in the 2520 it was officially replace by . Put in reserve by 2524, the Human-Covenant War was its lifeline: since UNSC needed all available ships at disposal, a number of Halcyons were retrofitted with proper systems and were launched in combat right away. The original, expensive structure proved to be also the most effective in the war, because it was capable to maintain an Halcyon operational even in case almost 90% of the armor was lost, an impressive capacity that forced the Navy to retrofit all eleven Block I cruisers.
Nonetheless, the scarce number built, which in the Block I case was even lower, meant that they hadn't much effect on the tide of the war. The last operational cruiser, the UNSC Pillar of Autumn, was further improved in 2552 and during the Fall of Reach, first, and the Battle of Installation 04 later, it proved how the original superstructure was useful, if used correctly: in fact it had a killing ratio far above its displacement, outmatching that of any UNSC ship ever built.