so from what i've heard the dark brotherhood contracts are unlimited but if this is true will you just keep killing until all non-essential npc's are dead?

A random npc is generated each time the quest is initiated. You won't be wiping out Skyrim's population.

No no no

The radiant quests to kill random npcs at the end of the quest line.....are picked from a list of a dozen especially supplied marks.......not your regular npc community.


The side quest kills ARE however npcs known to you throughout the game and killing some of them will terminate those npc specific help quests e.g.

Moving to the Spoilers forum, just in case