Portals are magic teleportation devices that allow a user to leave one hex and enter another instanly.
It seems using a portal doesn't follow the classical Movement rules since it would disallow using one by night or off Turn.Erf-b1-p046 Yet, the linked Maggie-Wanda-Sizemore and Parson use Gobwin Knob's portal to the Magic Kingdom during the turn of the Royal Crown Coalition.Erf-b1-p136 They then return to Gobwin KnobErf-b1-p142 a few moments before the start of their turn.Erf-b1-p144 Also, a unit of another side is shown using a portal during Gobwin Knob's turn.Erf-b1-p013 In addition, using a portal must not cost the portalling unit any move, as Parson, with a move of 0, is able to use one without any of the problems associated with crossing hex boundaries. Likewise, the casters left in the Coalition's turn, so they would not be otherwise able to leave the hex.
There may be limits on who may use Portals. It is implied that Warlords that use a Portal to the Magic Kingdom are disbanded;Erf-b1-p140 whether this is a portal feature or a Magic Kingdom specificity isn't cleared.