Jund Cataclysm

Sorcery

Each player sacrifices all creatures they control. Each player gains X life, where X is the total power of creatures that player sacrificed this way. If an opponent controlled more creatures than you, that player gains twice the amount of life, and you gain half as much life.

"The damned shards; everlasting separation from the medium of balance and control: it's well past due for a correction."

Continue!

Apex Regisaur

Creature - Dinosaur

Trample

At the beginning of your upkeep, you may draw cards equal to the power of another target creature you control. If you do, tap ~, and sacrifice a creature with power equal or greater to the amount of cards drawn this way.

Whenever ~ attacks, create three 3/3 Green Dinosaur creature tokens with Trample tapped and attacking. This ability only triggers once each turn.

9/9

"Large tracks have been sighted in the area. The sheer size of a creature that makes such tread...truly must be...." - Lost Explorer's Notes

Wild!

Realign the Hedrons

Battle - Defense

At the beginning of each player's upkeep, they may create a 1/1 Eldrazi Scion Creature Token, or a 2/2 White Kor Ally Creature token.

Ally and Eldrazi creatures gain unblockable as long as ~ has 1 Battle Counter on it.

Whenever ~ has 5 or more Battle Counters on it, you may sacrifice it. If you do, search your library for X Ally Creatures and put them onto the battlefield, where X is the number of Ally creatures you control. Exile all Eldrazi your opponents control.

When the last Battle Counter is removed from ~, each opponent may search your library for a creature and put it onto the battlefield under their control. It becomes a Colorless Eldrazi creature in addition to its other colors and types.

Continue, or create another variant of battles!

Syilkvaar of the Lost Woods

Legendary Creature - Elder Demon

Flying, Lifelink

At the beginning of your upkeep, sacrifice a creature other than ~. If you can't, tap ~, and you lose life equal to its power. If you do, put X +1/+1 counters on it, where X is the sacrificed creature's power.

At the beginning of combat on your turn, you may untap a target land you control. Until the end of the turn, it becomes a X/X Dryad creature that is still a land, where X is ~'s power.

6/6

"The woods outside the village have long been suspect of the missing lamb or cattle, but none dared stop the animals from carelessly striding in. It was only when the arbor branches wove and snapped, that the villagers decided against any such preventative measures."

Tried to go for a Pagan deity inspired angle, curious to see if it works or not!

Next challenge is similar but different; create another off-color pair or identity for a creature type such as the last challenge!