Portal chess

Portal chess is a chess variant which uses at least two fairy pieces called "portals" (or less commonly "portholes"). These pieces can be easily added by using poker chips, coins or other suitably sized objects. The game seeks to incorporate portals to allow pieces to teleport around the board. Apart from the portals and their ruleset, the game often plays like ordinary chess, including "en passant", castling, and pawn promotion.
Versions.
There are three versions of portal chess, created seemingly independently by three different people: David Howe in 1997, Mike Hidden some time before 2008, and Ian Buckley around 2012. They all, however, contain the core dynamic of "teleportation" and special squares/pieces for this, as opposed to other variants which allow transportation at any point and/or any time.
Throughout the article, the symbol "→" will be used to denote teleportation from one square to another.
David Howe version.
In this version, there are two distinct playing areas linked by "fixed portals". These areas can be either two separate boards or one board split down the middle (between the d- and e-files).
The rules that are different for this variant are:
Mark Hidden version.
The portals in this game are "neutral yet mobile".
The number and starting location of these portals can be different when the game begins, but the image shows the standard set-up.
In this game the portal pieces move around by very specific rules.
Ian Buckley version.
This version of the game has "player-controlled portals", which are linked to each other.
The rules for these portals are worked out as though they make the squares they cover into one square. In the set up to the right, a5 and e4 can be conceptualized as the same square.
The specific rules for portal use are as follows: