The I.K.S. Klothos, undergoing ship conversion from a D5 Battlecruiser to a modernized D7 Battlecruiser after the Battle of Caleb V.
This is my Second Entry to the Star Trek: Ships of the Line 2016 Calendar contest.
I always had a fascination with Klingon Lore. One being the Battle of Klach D'kel Brakt, that Kor participated in, which ended the Klingon-Romulan Alliance. But one aspect that came about my writing of the story of the Battle of Klach D'kel Brakt, was the story of the I.K.S. Klothos, which was first seen in the Star Trek the Animated Series (TAS): The Time Trap, but was depicted as a TOS-Era D7 Battlecruiser, and not the D5 Battlecruiser that was mentioned by Kor in Star Trek: Deep Space Nine: Once More Unto the Breach.
There are many different interpretations of why Kor wasn't accurate. Senility, two different ships named I.K.S. Klothos, or simply that some D7s were called D5s in those days. But to me, I have the impression that the Klothos could've gotten a ship conversion from a D5 Battlecruiser to a D7 Battlecruiser. This based off real ships during World War 1 and 2, where ships were converted in the war effort to something entirely new. Like some old Battleships becoming Aircraft Carriers and Cruise ships becoming Light warships (most Submarine Tenders).
So my lore is that Klingon Warships all share similar core architecture, where from the bridge down to engineering is the same on all Klingon warships from the D4 (the original design John Eaves made for Enterprise, but never aired), to the D5, the D6 (watch Prelude to Axanar), the D7, and finally the K'Tinga. Which would be expected of the Klingon Empire, which is ran on a war economy. For construction was be significantly faster in not having to retool for newer equipment.
The Klothos has the non-core equipment stripped, the framework extended for the D7 layout, the D5 engine replaced with the D7's S-2 Graf Engine, stronger hull, stronger shield generators, and the best Klingon Ship Disruptors money can buy.