Where do you find the keystone to give to cyrus?

Go to area 3 nessa then go south. There will be a bilding and go through it until you find some stairs go up them and you will find yourself outside. Go left up some more stairs and into a green circle walk into it and youll be in anouther ruin go through it,then you will come to 2 doors go in to the the bottem them keep going until you find more stairs go up them and it's in that room
Hope it helps

Nessa area three
Go NORTH and WEST
Find ruins
Go through ruins
Go out of ruins(that is only ruins part 1)
Go WEST onto teleporty green circle thing
Go WEST until room with 2 circle door things
NORTH door takes you to battles and minerals
Take SOUTH door to path
Go down and follow path to second teleport thing
Use teleport thing
Go up
Press 'A' on blue thing turns out it's the keystone
Yay no boss
I hate this mission now because you later need to get it back...