Deadly Silence (A Percy Jackson and Avengers Crossover)

Nico is an assassin, after Bianca died the greif broke him, he fled from camp and started taking out his revenge on select Demigods and Hunters, but then he decided why stop there.

Now he works as an assassin, no one hears him come, no one notices him leave, no clues, nothing.

Shadow travel in, shadow travel out

He is a well know assasin but no police can ever catch him, he's as silent as a shadow, even the Avengers have been sent after him

The Avengers and Demigods work together trying to find this 'Shadow Killer'

But one day he is hired to assasinate a demigod, the person who hired him is unknown

The Unknown employer hired Nico to kill a certain demigod, not Percy, but a certain son of Apollo