Karkat’s session was actually a (fairly) normal one.

On this page. 

Ancestors are a concept in troll society that are responsible for contributing a greater proportion of their descendant’s genes than the incestuous slurry from which troll eggs are produced. They share their descendant’s signs, horn shape, and blood color. High bloods tend to put more stock in their ancestor’s existence while low bloods don’t usually care about them too much. Because of the reproduction process of trolls, ancestors are usually long dead before their descendant hatches. However, they may still be alive if they’re a long lived caste.  

Rainbow Drinkers are essentially the Alternian equivalent of Twilight vampires. They can withstand sunlight and radiate light. They can also run very fast. Kanaya and Porrim’s conversation in the Openbound flash games confirms that the condition is directly related to jade blood. Kanaya theorized that jade bloods developed the condition after being in the dark birthing caverns for so long while Rose theorized that they developed the abilities in order to scare away predators from wigglers. 

Aranea states here that blue bloods only occasionally have mind control powers. Vriska states here that yellow bloods sometimes have those abilities like Sollux and that telekinesis is common to rust bloods.  

The ancestors are the same Beforan trolls just under different conditions. This is mainly seen through the Condesce’s behavior since her and Meenah are very similar.

Yes, by using your Sacrificial Slab.

Jack Noir first used them to destroy the Dersite and Prospitian armies and part of the Battlefield in the Beta kids’ session. He then used them to destroy Prospit.

Jadesprite is Jade’s dreamself and she was prototyped with Bec so when Jade died on her Quest Bed, Jadesprite went godtier and she retained some dog features including his ears. 

Brain ghost Dirk is a projection in Jake’s mind that only he can see. He’s a startlingly close approximation of Dirk’s mannerisms and behavior based on Jake’s intimate knowledge of him. Jake can actually bring him into existence once he tapped his full Page powers.