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.
While chunk spawning always has a 10% success rate (not taking slime chunk chances or anything else into account), the success rate of swamp spawning depends on the light level (just like it is with hostile mobs) and the moon phase: Spawn Rate = 50% * [Light Factor] * [Lunar Phase Factor]