Protein hulk does he alow me to play any and all creatures in my library if there mana cost is 6 or lees or does the creatures total add up to 6 and cast those ones?
Its the sum of all mana costs must equal 6 or less. You may select 2 creatures with a CMC of 3 for example
JH has it right. You could get 6 creatures costing 1 mana each or 1 creature costing 6 or any combination adding up to 6 total mana. {Protean Hulk}
You could get 100 creatures costing 0 :P
Its been done. Flash Hulk had a version that got 4 {disciple of the vault} and cards with X for a mana cost, that when cast for 0 would die. Also things like {lotus petal} etc that could be destroyed for free dealing damage
Sounds like good times with {Blood Artist} not sure what you would combo with it since I am a standard player, but I am sure you people can imagine up the rest :p