"The warriors killed Kahless."
Translation:qeylIS luHoH SuvwI'pu'.
The plural markers are not required (except in some unusual circumstances). The unmarked noun could be singular or plural. SuvwI' could mean "warrior" or "warriors". SuvwI'pu' can only mean "warriors". When the plural marker is not there, usually context will make it clear whether the singular or plural is meant. And, in fact, the lu- prefix in this sentence makes it clear that the subject is plural and the object is singular, so using the -pu' plural noun suffix adds no additional information to this sentence.