Mal Magog-Kollus and Gol

Firstrike. Vigilance. Daunt. Immune to deathtouch.
Destroying or exiling Mal Magog permanently reduces his toughness by 5 instead. Mal Magog cannot go to your hand.
When you need to sacrifice a creature Mal Magog creates an Undead Giant token. Mal Magog cannot be tapped. Mal Magog attacks every turn. When Kollus and Gol kills a unit he creates a land "Death Energy". Creates 1 mana that must be used only on Mal Magog's abilities.
{x}{x}{x}{x} Create X Undead Giants.
{x}{x} Destroy target creature with