1. What is it?

Mortality is the acknowledgement that with life comes eventual and inevitable death.

In literature mortality usually describes a character contemplating death and the fragility of life.

2. How is it made?

3. Examples in literature

Sleeping at Last 
by Christina Rossetti

Sleeping at last, the trouble and tumult over,
Sleeping at last, the struggle and horror past,
Cold and white, out of sight of friend and of lover,
Sleeping at last.

No more a tired heart downcast or overcast,
No more pangs that wring or shifting fears that hover,
Sleeping at last in a dreamless sleep locked fast.

Fast asleep. Singing birds in their leafy cover
Cannot wake her, nor shake her the gusty blast.
Under the purple thyme and the purple clover
Sleeping at last.

The Snows of Kilimanjaro 
by Ernest Hemingway

Excerpt:

“How do you feel?” she said. She had come out from the tent now after her bath.
“All right.”
“Could you eat now?” He saw Molo behind her with the folding table and the other boy with the dishes.
“I want to write,” he said.
“You ought to take some broth to keep your strength up.”
“I’m going to die tonight,” he said. “I don’t need my strength up.”
“Don’t be melodramatic, Harry, please,” she said.
“Why don’t you use your nose? I’m rotted half way up my thigh now. What the hell should I fool with broth for? Molo bring whiskey-soda.”
“Please take the broth,” she said gently.
“All right.”
The broth was too hot. He had to hold it in the cup until it cooled enough to take it and then he just got it down without gagging.
“You’re a fine woman,” he said. “Don’t pay any attention to me.”
She looked at him with her well-known, well-loved face from Spur and Town & Country, only a little the worse for drink, only a little the worse for bed, but Town & Country never showed those good breasts and those useful thighs and those lightly small-of-back-caressing hands, and as he looked and saw her well-known pleasant smile, he felt death come again.
in.
This time there was no rush. It was a puff, as of a wind that makes a candle flicker and the flame go tall.
“They can bring my net out later and hang it from the tree and build the fire up. I’m not going in the tent tonight. It’s not worth moving. It’s a clear night. There won’t be any rain.”
So this was how you died, in whispers that you did not hear. Well, there would be no more quarrelling. He could promise that. The one experience that he had never had he was not going to spoil now. He probably would. You spoiled everything. But perhaps he wouldn’t.
“You can’t take dictation, can you?”
“I never learned,” she told him.
“That’s all right.”
There wasn’t time, of course, although it seemed as though it telescoped so that you might put it all into one paragraph if you could get it right.