Nefarox, Overlord of Grixis

Flying
Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.)
Whenever Nefarox attacks alone, defending player sacrifices a creature of their choice.

Demonic Rising

At the beginning of your end step, if you control exactly one creature, create a 5/5 black Demon creature token with flying.

Deadly Wanderings

As long as you control exactly one creature, that creature gets +2/+0 and has deathtouch and lifelink.

Homicidal Seclusion

As long as you control exactly one creature, that creature gets +3/+1 and has lifelink.

Shadows' Lair

(Transforms from Grasping Shadows.)
{T}: Add {B}.
{B}, {T}, Remove a dread counter from this land: You draw a card and you lose 1 life.

Grasping Shadows

Whenever a creature you control attacks alone, it gains deathtouch and lifelink until end of turn. Put a dread counter on this enchantment. Then if there are three or more dread counters on it, transform it.