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.
According to the minecraft wiki, this is there spawn routine: 1  Slimes naturally spawn in underground caves and on the surface of Swamp biomes during the night (or superflat worlds) 2  In swamps, slimes may spawn at night. 3  They spawn throughout underground caves below level 40.