Ancient Pseudoscience Station

The Ancient Alter is a structure that originates in the underground. Currently its only purpose appears to be to provide loot drops at random to the player. The lua file seems to allude to this becoming a new prototyping entity, like the Science Machine for science and the Shadow Manipulator for magic. This structure will allow a new category of crafting called "Ancient". The file used to house this structures texture is called "anim/crafting_table.zip", which definitely signals this as an item that players will be able to craft new recipes on in the future. It can be spawned by using:  DebugSpawn("ancient_altar")

When being struck with a hammer, it takes 6 total strikes to destroy completely, but that is not as easy as it seems. For each strike to the alter, it returns with lightning strikes to the ground all around the player, potentially setting nearby flammable mobs on fire. Each hit randomizes a certain "spawn" around the alter - these spawns can include loot (such as Gems, Trinkets, Armor, Weapons, or various Staffs), enemy mobs (Splumonkey, Cave Spider, Spitter, Baby Tentacles or Bats), along with the chance for a health buff (positive or negative). It can even spawn a Meat Effigy. It also appears to have a gradually strengthening negative sanity aura for each blow it is dealt. The aura stays with the player, regardless of distance moved away from the area of the alter.

Item Drops
None of these spawns are guaranteed to drop when the altar is struck, and the potential for each drop is currently very random.

Mob Spawns (and misc.)
There is also a likelihood of non-item based spawns occurring when striking the altar - these seem to be just as random as the item spawns, though the enemy mob based spawns appear to have a higher than average chance of appearing.