Greater Rift Keystone drop rate and requirements?

This may be just an approximate answer. But as far as I tested it, I've checked it on my game.

You reference that T6 will provide a 100% drop chance. As far as I tested it, this won't be true. I have played some T6 portals and I gt some keys, which is great, but also some runs without any key.

There is a reference on the net which says it could be 100%. But in my experience they are much lower. As everytime were a percentage chance exists, it won't be possible to pin it down to an exact value without viewing the code. But regarding my drop chance experiences the drop chance base seems to be like the drop rate for the infernal machine which is described below.

• Torment I: 25%
• Torment II: 28%
• Torment III: 33%
• Torment IV: 38%
• Torment V: 43%
• Torment VI: 50%