So glad you got to listen and learn a few things! Awesome you got a gold Skeleton Assasin! How hilarious is that?

Selenia Sky is a summoner. Summoners call their monsters to battle, but they can only summon monsters from their own splinters/nations. Selenia only has three dragons to work with in her splinter. She needs more monsters to play with, so she can summon monsters from any of the other splinters to fight with her dragons on her team. Only thing is, monsters cannot mix. So she can only summon one splinter at a time in addition to her dragons.

Hope that makes sense!