The phrase "a rather sombre" is correct and usable in written English.
It can be used to describe a mood, tone, or atmosphere that is serious, dark, or reflective.
Example: "The film had a rather sombre tone, leaving the audience in deep thought."
Alternatives: "a somewhat gloomy" or "a rather serious".
On the whole, though, it's a rather sombre tale.
Bacon's first Crucifixion uses a rather sombre and restrained palette, mostly black and grey.
Comte was a rather sombre, ungrateful, self-centred, and egocentric personality, but he compensated for this by his zeal for the welfare of humanity, his intellectual determination, and his strenuous application to his life's work.
Despite the upbeat attitude among the negotiators, who once again arrived at the Intercontinental on Wednesday, the lack of information led to a rather sombre mood among the much-reduced press corps.
Add in the fact that the size of the workforce of the developed world has started to decline, and will continue to shrink though to the late 2030s, and you can paint a rather sombre picture.
Rather than find fault with Cameron, he spends much of the pamphlet taking on critics of the Tory campaign (myself included), but he concludes on a rather sombre note.
Instead, this is a thoughtful, rather sombre look at the death of desire, sacrificed on the altar of comfort.
On top of that, he has an active, and rather sombre, fantasy life and likes to hint at a classified military past.
Comedian Phil Kay's on-stage antics have been shocking audiences in a rather less sombre fashion.
But Sunday's ceremony took a rather more sombre and political tone as stars lined-up to defend the BBC and criticise the government.
Take the rather sombre trailer for the upcoming, long-awaited film adaptation of Les Misérables, for example.
