Main Features:

• Adds the Moonlight back into the game. Each biome has a unique Moonlight color. Old PEAK versions used to have this, not sure why they removed it.
• Darker nights. Different biomes have different darkness levels.

Sub-features:

• Item light emission for items such as Napberries and Faerie Lanterns.

• Adding back the missing Lava Bubbles for Caldera and the Kiln, as well as Kiln's Embers and Smoke. The Lava Bubbles didn't work probably and only appeared when the lava surface in Caldera was at its lowest level (probably why the devs disabled it). Now they follow the lava surface up/down.
• And some more tiny features, but you can find out as you play.

Notes:

• Enabling extra lighting does eat some performance but only if you spam 6+ dynamic light sources in close proximity. From testing, using items such as Lantern, the real performance eater is the fake glow that was introduced in The Last Ascent.