The
item enhancement system is important to get into, particularly if you are moving into Hell difficulty (
see Preparing for Hell on the Player Tips page also) - note Cow King no longer drops the D-Stones every kill, but Anya quest gives you a half dozen a time.
Dragon Stones are one part of this. Dragon Stones can be clicked to cyclically turn into a series of different item (D Stone, Spider's Silk, Forging Hammer, Tyranium Ore etc). These can be used to combine with any item (including runewords and uniques) to give additional stats. Each item can only have one stat enhacement but it can be done multiple times.
Go to
this link (ES Cube Recipes) , which is worth bookmarking. Click on
D-Stone at the top.
It's recommended that you use as many D-Stones as you can find to boost the 'Increase Max Life 4%' stat on each item.
i) you can do it many times on each item - you'll need a D-Stone for every additional 4%;
ii) its capped how many times you can do this eg if its capped at 60% you can do it 15 times - if you go beyond this it will eat the D-Stone);
iii) note that it also increases the level requirement on the item each time you repeat the process.
I used all the D-Stones I found and raised my life from 700 to 3k plus on a Sorc - its needed because mobs do hooj damage in Hell difficulty.
Apart from D-Stones there lots of other recipes to raise skills and stats at the above links.