Please note that the Mob Spawner has not been created as a means for you to collect tons of loot, so this is not how it works.
The Mob Spawner is an item mainly intended to create game content for other players, for example within Adventures.
For this purpose Creatures that can be spawned will not contain any loot, except for stuff that you yourself can provide for the first Creature that will spawn.
- crafting an LED (a light cube that can be set to a large number of colors) after crafting a Wood Burning Lamp, Wiring Tool and Switch, plus
- crafting a Pressure Plate
Afterwards each Mob Spawner can be crafted with
- 5 Arcstones that can mainly be obtained from Keepas of any kind, either by killing and looting them or by taming, feeding and harvesting from them
- 2 Iron Slabs, created by putting Iron Bars into a Processor
- and 3 Bones that can either be obtained from nearly any Creature by killing or pet-harvesting, or alternatively from blocks of Fossils put into a Processor
Creatures spawned by the Mob Spawner will always appear directly over or in front of the Spawner (depending where you direct it/make it "look") at the nearest possible free space.
Similar to Loot Spawners you can place Mob Spawners under floors, behind walls and over ceilings too to hide them. However please note that Mob Spawners placed upside down (on/behind ceilings) might not work every time, so it's better to avoid using them this way.
If you want the first creature that will spawn to drop specific loot, you will have to put this loot into the according storage window by right-clicking the Loot Spawner after placing it.
In this way you can "fill" the first spawned Creature with all kinds of loot including crafted items and liquids that the Creature will then drop when being killed by a player, to challenge and then reward other players, for example within Adventures.
The Mob Spawner will only work after being placed into the world and wired to at least one activation device like a Sensor, Switch, Number Pad or Pressure Plate. It cannot simply be activated by clicking on it like any kind of Lamp could be.
If you right-click on the placed Mob Spawner (or type "f" as the default key to activate it), a storage window will open that you can then fill with loot. As mentioned, only the first Creature that spawns will have this loot inside and will drop this loot in a Loot Bag if a player kills it. However all the following Creatures that you can also make to spawn will not contain loot.
The settings of the Mob Spawner can be defined by using an equipped Wiring Tool and typing "n" (default key) while looking at the Mob Spawner. Then a window will open to:
- let you choose the exact type of Creature that you want to spawn,
- to define if the Creature should be peaceful or aggressive (with a lot of exceptions, see below)
- and to decide if you only want the Creature/s to spawn after providing them with loot (or not)
Please mind that aggressive Creatures can not be set to be "peaceful", they will only automatically be peaceful when spawned by Mob Spawners on worlds where the "peaceful Creatures" options is enabled (one of the "Pro" game world options).
If you enable the setting "requires loot", only one Creature will spawn after you've put some stuff into the storage window, and this Creature will then drop all the stuff that you've provided when killed. You cannot split the loot to make more than one Creature drop it, and you cannot multiply the loot this way.
The Mob Spawner will not spawn Rockzillas, Night Hoglets, Night Twiggies nor any kind of Keepas, but it can spawn ghost creatures that were introduced for Haunted Nights (seasonal Halloween event). To spawn Rockzillas, you will have to build the according altars that will make them appear like usual.
Since update R39 even peaceful Creatures can be set to be aggressive when spawned by a Mob Spawner, even on game worlds with the "Pro" world option "peaceful creatures" enabled.
Exceptions are all Ghost Creatures and common greeen Leafies - these will always be peaceful; ghosts will even run away from players when these approach them.
Kindly note that the Creatures that spawn will have their usual behaviour, weaknesses, strength and toughness depending on the combat difficulty settings of the world (medium by default).
This means that aggressive Creatures will attack your player character when you're close enough, no matter if you were the one who placed the Mob Spawner or just the one who made them spawn. You can still make aggressive Creatures spawn around your base like watch-dogs, as long as you know a safe way into your base or can disable the Mob Spawner with devices like Number Pads (for example).
Health bars, combat abilities or damage dealt by spawned Creatures cannot be increased or decreased by using the Mob Spawner, so be aware of spawning tough monsters (like corrupted ones) without being prepared for a fight.
Night creatures and some underground creatures spawned by the Mob Spawner will burn away in the sun like they usually do; with the only difference that they WILL leave their Loot Bags behind filled with the loot that you have provided them with, even if they have not been killed by players in time.