Actually.... The last Duel with Damamu was against Chupataro in Arc 7, but it was a Duel that was only half shown. However, the other Duel Damamu had was against Yuga at the end of Season 1, but Damamu was weakened because Zwijo was using Earthdamar against the Main Group. Therefore, Yuhi took Damamu's place to confront Yuga. However, this Duel is a reference to that Duel between Yuhi against Damamu in Yuamu's body. You could even say that it was a stolen victory that Yuhi was able to recover in this Episode. In fact, Tamabot Deck was part of Yuhi's Deck, but slowly Yuhi began to distance himself from it. It is a good way to show Yuhi's growth as a Duelist since the Tamabot Deck represented the childish side that Yuhi had in the previous Seasons.

On the other hand, CPT got its revenge against Epoch/Manabu and those inferior beings by taking them to enemy territory. Perhaps the question would be how did CPT gain access to Dark Matter Space, but I wouldn't be surprised if it was because of Curry (in fact, I wouldn't be surprised if CPT is the one who tricked the Dark Meister at the end of Episode 111 and not Zwijo as some would think) PS: RIP Damamu. They went back to being an ordinary Earthdamar. Something similar had not happened since Arc 4 in Season 1. It is also interesting that they have shown Damamu's ability to shapeshift and take on the appearance of other People (very similar to how President Drone could shapeshift into different objects as seen in SEVENS)

I'm not sure if anyone else has thought of this, but: What is the dark matter empire is made up of rejected prototype Velgearians? Maybe they had defects and ended up dissolving into pure darkness instead of living with a galaxy within them. Is it possible that something awakened them (like the usage of Monster Reborn) and now they're trying to find life like the Velgearians had? That might be why the Dark Meister is interested in the curry bread, to get ahold of Earthdamar. She probably witnessed the duel between the Ohdos and decided to take Yuamu to assist her. It's also possible that the Dark Matter empire are a different race just wanting to step out of the darkness I admit, I haven't completely thought this out. I just wanted to share my first thoughts after rewatching 109