While Jokulmorder's mana value is great compared to its size, the true cost of this creature comes alongside the fact that you have to sacrifice five lands once it enters the battlefield
One last consideration to think about when looking for team pump spells is your creatures access to evasion to push damage through enemy blockers
I control the black creature [c]Demon of Loathing[/c], the artifact creature [c]Palladium Myr[/c], and nonblack nonartifact creature [c]Thorn Mammoth[/c]
The transformation cost is too high, and even then, you don't get too much benefit
The cost is huge, but what you get for it can be pretty amazing
Cast a spell, wait some turns, then its cast again and you reap the rewards