I haven't seen any other threads on this, so note these tantalizing previews:
Otto Kronig is basically just a better version of Goblin Builder but without the ability to construct things (he just repairs/improves them). Not sure I would take the time to summon him except in a conjuration swarm deck (which I am hoping will become viable with the new warlord). I like that his reinforce ability is a quick action.
As best I can tell, the other cards are
"Brace Yourself" - Looks like something that takes effect once and is then discarded, probably as a defensive effect.
"Harshforge Monolith" - Well, it is Zone Exclusive and affects all enemies (presumably just the ones in the same zone). It is also really cheap, so I am guessing that it is not epic.
"Disarm*" - Perhaps this targets equipment? It references an object though. The X casting cost makes me think it is a counter-card.
Just speculation, naturally.