What makes Call of Cthulhu (CoC) different from a typical game of Dungeons & Dragons (DnD) anyway?
The key factor in both Dungeons & Dragons and Call of Cthulhu is MOTIVATION. This is also the factor that distinguishes between the two. It may be a sutble difference, but if the Storyteller and the Players can grasp the difference, then Call of Cthulhu can come alive during gaming sessions.
Motivation is what drives the characters within the game to act. It’s what makes them take part in the story being told within the structure of the game.
All Dungeons & Dragons characters, regardless of species, alignment, or adventuring skill, can be assumed to want to kill monsters and take their treasure as a means of increasing their own personal power. It’s the typical idea of kicking in a door, killing the monster, and taking its treasure. In finding treasure, the charcters buy cool magical items and gain XP to get more and more powerful.
All Call of Cthulhu Investigators, likewise, can be assumed to be actively investigating, which is to say seeking out (or at least not actively avoiding) occult mysteries to solve as a means of defeating (or at least stalling) servants of the evil alien god Cthulhu or similar monstrosities. The goal here is not to gain XP to get stronger. The goal here is simply to SURVIVE.