Steve's seventh costume is based on the Zombie, an undead Minecraft enemy who often appears in groups.
The stage's nighttime cycle references how the Zombies appear as enemies during the nighttime cycle in Minecraft.
The first battle condition references how the Zombies feature low speed but can occasionally wear armor to reduce any damage from the player.
The Zombie starts off with 20 HP, referencing the Zombie's 20 health points in Minecraft.
Other trivia:
This spirit's Fire Weakness ability references the Zombies' vulnerability to sunlight, where they will catch fire and disintegrate.