Upgrade simulator — what will this chain cost me?
Pick any armour or weapon — say Iron Plate Armour — set a target level, and it walks each step with the true chance and material list, rolling failures exactly as the server would. Fail a +7→+8 attempt and the sim continues from where you landed, not where you hoped: that's the difference between "about 200k yang" and the real number. Every step names its items, so you can shop before you click.
Reroll calculator — which applies can this item roll?
The pool explorer lists every possible apply with its per-level range — try Wooden Bracelet to see a low-level item's spread, then flip the rare toggle for the second line. Each row shows the roll weight and expected value across the reroll distribution, so "should I keep this and reroll the other line?" becomes arithmetic instead of folklore.
Drop explorer — where does this drop?
Search an item — Bear Gall among them — and it lists every mob and stone holding it in their loot tables, with chances. Reverse mode starts from the mob and asks what it carries. Chances are the true table values divided out to per-kill odds, not the rounded numbers other sites print.
One more: Dragon Stone alchemy
The Dragon Stone calculator tabulates each stone's base apply by grade — pick your diamond shape and see exactly what it adds at levels 1 through 6, no guessing from blurry screenshots.