One couldn't make out what the dark mass was from a distance.

远处黑压压的一片，看不清是些什么东西。

《新英汉大辞典》

Night enshrouding the earth, nobody could make out what the dark mass was from a distance.

黑夜笼罩着大地，谁也看不清远处黑压压的一片是什么东西。

youdao

Yet this palaeontological paradise holds a dark secret: the mass deaths were not caused by a single event.

然而，这片古生物乐土却隐藏了一个秘密：如此大量的死亡并不是一次事件导致的。

youdao

Below is a dark mass of seated spectators.

WSJ: A Dizzying Artistic Feat | Edgar Degas | Miss La La at the Cirque Fernando | By Karen Wilkin

He ran a hand through his dark hair, a shaggy mass that flopped in several directions.

NEWYORKER: Midnight in Dostoevsky

The same is true for lots of games and especially those with loyal followings like Mass Effect and Dark Souls and and the big shooters with their outrageous map-packs.

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