I released a new mod called Beyond the Stars which has some stuff from The Deeplands Mod but reimagined:

https://www.curseforge.com/minecraft/mc-mods/beyond-the-stars

A new and stable version for the mod is also currently developed but there currently isn't a release date.

Note: This mod is currently in alpha and issues may happen.

You enter the dimension by making a frame out of Golden Scoria Frames and light it with Golden Dust

After entering the portal you land in an giant cave full of biomes, structures and other new stuff.

You start by getting wood (through roots and mushrooms) and collect ores to combine them to some more powerful tools (but not as powerful as diamond) with some special abilitys like mining as fast as gold. You can also find diamonds at the roof of the dimension which has no bedrock ceiling. After that you should be powerful enough to face some stronger enemies.

You can fight to Bosses currently with a third one currently being W.I.P.

The Elder Ghost (Bronze Boss)

Can be summoned by putting a Eternal Flame on a Broken Pedestal that can be found in Graveyards.

It's a blue Ghost that shoots something called Ecto Goo at you. If it doesn't hit you it sticks on the block it landed and spawns a normal ghost after a while.

The Starmage (Silver Boss)

This Wizard is spawned by Right-Clicking the Staraltar found in the Startower.

He casts some magic spells on you or creating mimics of him self.

The Rune Guardian (Gold Boss) W.I.P.

Can currently be found nowhere.

This creature throws runes on you to damage you.

Some cool mod showcases:

https://www.youtube.com/watch?v=q5-GYbUmGLQ by mr_Cripras

If you want to leave any form of critisism, found an issue or want to suggest a feature leave a comment :) .