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.
They can also spawn in swamp biomes between layers 50-70 in light levels of 7 or less. Slimes will not spawn within 24 blocks (spherical) of any player, and will despawn over time if no player is within 32 blocks and instantly if no player is within 128 blocks.