I know the first two questions are still foggy, but here's a quick question to aggravate another player. Teleport needs a target creature, and target zone. If LOS is blocked, then you can't proceed in that direction with the teleport, correct? So hypothetically speaking, if someone took the time to box you in with two-four walls of stone, you have to fight your way through them with no good way of escape?
If you aren't playing as the Wizard, or Forcemaster then yes, there is no way of using teleport to escape.
However, the Wizard has Huggin who can cast Incantation spells, and the Forcemaster has Thoughtspores which can have an Incantation spell bound to it. Both of them are flying, so they can see the entire board.
Of course a Blue Gremlin could also teleport through since it doesn't need line of sight.
Don't know if we'll ever see any other color of gremlin, or what their abilities might be though...