Requiem Antiquorum

Across your journeys, you'll eventually encounter the Void, a twisted realm whose sole purpose seems to be the eternal torment of those within.

Extremely far down the line of progression, brick pyramids may be found in the realm of the ascended, the Higher Plane, which were a structure added and removed in vanilla infdev.

A giant, igneous complex of ancient structures buried deep underground. Whoever built them possessed unrivaled technology, yet not one of their denizens can be found...

Requiem adds many new redstone components. One of them is shown above, the heat sensor, where it is being used in a redstone clock with a random duration.

Likely the first new structure you'll encounter. It contains some modest loot, as well as a slime spawner that clever players could put to use.