"This item will now randomly appear in runs". What does it mean?

[- Yor]

Title says it.
What does this message that I receive means? As far as my runs went, I didnt get any items except from chests or printers

[Lt. Dan's Legs]

You unlocked an achievement or item, and from now on it has a chance to randomly appear in your runs.

[InstableMonster]

It means exactly what is written, which word dont you understand?

[Thqwib]

Items you find are restricted to a set pool of what can and can't appear during your run. Completing a challenge will add previously locked items to your pool of what can appear next time you open a chest, use a shrine of chance, etc.

[Draco18s]

Notably locked items are on average better (about 33-33-33 green, red, and orange (Q items)) than the default set (90% white tier).

[Ivara Ara]

Originally posted by InstableMonster:

It means exactly what is written, which word dont you understand?

[Lunacy]

It used to not ever drop before.
But now it will drop from chests occasionally.