Silumgar, the Drifting Death is Dimir colored dragon tribal commander. It works as a great blocker due to flying, deathtouch and hexproof. The most important part of Silumgar is the dragon tribal ability to give -1/-1 to opponents creatures, whenever a dragon you control attacks, making Silumgar a real threat in Dimir due to high amount of changelings, copies and a few actual dragons.
Dragons, alongside Goblins, are reds primary creature types. Dragons are reds strongest creatures and most of the expansions have some kind of red dragon in them. As dragons are expensive to cast, dragon tribal decks run multiple cost reduction effects and have ways to cheat the expensive dragons on the battlefield.
Reanimate decks brings back creatures from the graveyard straight to the battlefield. The reanimated creatures are often expensive to cast, like demons, and are complete haymakers compared to the reanimation costs.
Mono blue has multiple ways to clone own or opponents permanents. The gameplay changes effectively, when you get to play your opponents biggest threats, too and clone decks can lead to some very weird and interesting situations.