Sossedov is a metaphorical term for the 'dragonblood'. Dovah sos is literal dragon blood, from actual dragons. The sossedov refers to the power we have, dovah and dovahkiin alike.
Some of ours can be hostile, and those are typically the ones I deal with. Once I've killed them, they can never come back because I absorb their life force and knowledge into myself, just as any other dragon would do.