I have a magic item I'm putting together and it needs some form of trials to attune to. I want the item to try and weed out those who would not save others - the selfish and unworthy, basically.

One thought I had was for it to seek out the characters greatest goal, their aspirations, and offer it to them in exchange for the death of one person.

I also considered using the Adventure Time heroes trials thing of giving them the quest to slay a goblin, who will be annoying but not hostile.

The trials will take place inside their mind, and so self sacrifice is something that can happen without real-world consequence. They can die to save someone, as the ultimate sacrifice, and it'll work out (though I will prolong it so that people think they have actually died, because I like to make my players feel things!)

I need it to be quick, and I need to hopefully make it poignant or deep if possible. I welcome any ideas!

You could do some with no right or wrong answer, just to make them think about what they would do. Like the trolley problem, or two loved ones drowning but they can only save one, who do they choose. 
Or, of course, the kobayashi maru to show them sometimes they’ll fail.

And they need to explain their reason to whoever is running this trial, and the explanation is the real trial.