Parallel drainage pattern. A parallel drainage system is a pattern of rivers caused by steep slopes with some relief. Because of the steep slopes, the streams are swift and straight, with very few tributaries, and all flow in the same direction.
1 In Creative, the player can use spawn eggs to spawn most mobs. 2  When mobs are spawned this way, all normal spawning requirements, such as light level and block type, are ignored. 3  Any entity can be spawned using the /summon command.
Levels of Light. The level of light determines if hostile or passive mobs will spawn. For example, a Cow will spawn above light level 7 or higher on Grass blocks. This also works for Pigs, Chickens and Sheep. Hostile mobs, such as Skeletons and Zombies, will spawn in light levels 7 or lower. A player may keep mobs like this from spawning in an area by blanketing the area with torches.