Future Klingon warship

Star Trek: The Next Generation
Episode: TNG 278 - All Good Things... Part II

In an alternate timeline, influenced by Q and created via a temporal anomaly, this future design of Klingon vessel attacked the U.S.S. Pasteur after that ship entered the Neutral Zone.

The future Enterprise-D came to the Pasteur's aid, quickly dispensing with the Klingon threat.