This combo only works in commander because of the fact that your general can go back to the command zone instead of the graveyard.

I built this around elves that tap for glorious amounts of mana, along with as many untap effects as I could find to build up massive amounts of mana. Go infinite mana if you want, but you don't need to.

Let's say you have 60 green mana. Omnath now has 61 power, so if you sac it to Altar of Dementia, your opponent will mill 61. When you sac it, put it in the command zone. Oh no, Omnath now costs 2 more to cast. Spend the 5 mana to cast him again, now you have 55 mana, and a 56/56 Omnath. Rinse and repeat for mill!! If you have an untap engine for one of your elves, you can refuel him when you cast him again and take out multiple players if you like.

I also have greater good and momentous fall, so that I can randomly draw 60 cards to find a kill card. So much fun.