U mean All i need is to get all Treasure Chest Items ? or If i only got 1(last) treasure key ?
Okay, I was joking around there. There is no way of guessing which Treasure Chest item you will get until you run out of items. Here is an example. Johnny has ten different colored marbles in a small bag. He reaches in to grab one. He gets a red, but he wanted green. So he keeps trying and trying until either he runs out of marbles in the bag or he gets the green one.
Say there are 100 different items you can get from the chest for example (there's more like 120 really).
If you open one chest that's 1 in 100 odds you get the item you want first try, 1 in 99 odds on the second try (don't delete the chest items or your odds will ALWAYS be 1 in 100) if there are three chests left your odds are 1 in 3, with 2 chests left you have a 50% chance to get the item you want, and if you have HORRIBLE luck and the last chest has the item you want it's 100% you'll get it once you have EVERY other item the chest can drop.
You can get the Caladbolg alter on your first try with a free key if you're lucky, if you aren't lucky you can spend a maximum of about 21,000 AC opening every chest. I personally went through about 16k AC (earned on AExtras) before I got my alter.