Many people had trouble so I will I think help. Remember, he blocks critical, but not all the time! Once you have some death shields on, you can use feint and traps and buff up. Even when he puts traps on you, it will do very minimum damage. Wraith is very good in this battle, so put some in your deck. You need a death prism, but if you buff up and trap enough, A couple will do. I found that the minion was good because she used small rank spells such as ghoul which took away the traps he put on. I killed her last because I focused on Osseus. He has about thirteen thousand life, and the minion has one thousand ten. Wraith, feint, shield, death prism and your on your way to skeletal dragon!
I finally defeated Osseus at level 68. I used the grimcather deck and also put at least 6 prisms in, put one on the minion and built up my pips, put on vengeance had 3 lots of charms on and got rid of her in 1 spell. Also I had to counter Osseus helping hands in my amulet and as a death main and life secondary I put sanctuary out. I also had a cloak and shoes which not only boosted me in health but went critical. When you get him down to under 4500 health he starts making a lot of mistakes and does not cheat anymore as he knows he will be defeated. So I wait and put on charms and lots of prisms and used my life spells on him as they are also a boost. I did not worry about my health at all. It took me 6 attempts to do but I finally did it. The skeletal dragon is awesome and also I received Dr Von's monster which is also awesome.