Is there a block or mod that will simulate a player, for the purposes of mobs spawning and staying spawned?
I have a zombie spawner, with a protected villager nearby. The mobs try to walk towards him but get trapped in a pit in front of a grinder for mob essense.
But of course it only works when one of us is within XX blocks.
Is there a block I can use to simulate the presence of a player?
I don't know of anything that can keep mobs from despawning instantly when there's nobody within 180 blocks, but I do know of a workaround.
Mobs will only insta-despawn if there's a player in the dimension, but not within 180 meters, which I assume is so you can't make the pigmen chasing you through the Nether vanish by stepping through the portal. So, if you set your mob farm up in its own dedicated chunkloaded Mystcraft age, you won't have trouble with the mobs disappearing, if you can find a way to spawn them in an empty age.
This problem can most easily be solved by planting some Cursed Earth (from Extra Utilities) underneath a Vanilla spawner. This won't run as fast as a Cursed Earth-free spawner with a player nearby, but it'll still run. There's also a number of modded spawners that work without nearby players, but all the ones I know about take energy to run, if not some additional reagent as well (such as Mob Essence, in the case of the MFR autospawner).
So, if you're using Vanilla spawners, you can make it work whenever the server is running by putting Cursed Earth under the spawners and building the farm in its own age with a chunkloader.