Tv Series: After an explosion opens a hole in Hell, allowing demons and unknown creatures to escape, the son of the devil travels to Los Angeles to bring them back before they overrun the world.

mikepedley85 means that his goal -unless stated- would be to let the demons overrun the world “..his reasons are his own..” needs to be spelled out,
for instance-
When demons escape hell, the son of devil must bring them back to prove himself a better guardian over his elder brother
Although I have a love-hate relationship with the TVS format, I am interested in its differences from loglining for a feature film. So it must have enough juice to last a dozen hours & can be structured into Three Act for every episode. But when it comes to the whole, Is it the Second Act which must be elastic enough to bring most of the plot?
If so, the action of “..must bring the demons back..” is the second act. It paints a very specific premise which dictates the nature of your TVS. It becomes a narrative of catching demons. This is how your trailer would look like. This action will determine the kind of audience it attracts.