From the preview:
Some mages in the early days of arcane study, discovered the ability to pull elementally attuned creatures from across the world to their location and follow their commands. Known as Summoners, these wizards specialized in evocation and learned to harness these creatures for specular effect. Most interesting of the creatures they can summon are the Lunarians and the Demonites. Lunarians, as denizens of Numina’s Moon are the first extraterrestrial creatures to visit Terra, and despite their sentience, readily follow a Summoner’s command during their evocation period. Demonites are a far more wicked creature, summoned demons from beyond the dimensional planes placed into inanimate objects, and Summoners must give much of themselves to create the puppets for the demons to control.
The Summoner lacks any real combat capability, but their summons provide a variety of monsters for them to command, and support. Though they can only have one summon in play, the Summoner can force them back to their realm and create a magical spell at the same location, creating a ‘bomb’ out of their Summon, before calling in another for backup.