Large Locked drop question ?

[ujangkampak]

156468

My first time drop the Large Locked by killing boss at gnomish ruins normal maps, just lucky got it without reroll :D
My question, is the large locked drop has specific maps / boss , or have a chance drop in all maps / boss ?
Thanks :D

[Ninthplague]

I was getting massive cryostar crate in elite underhul before