I don't understand, how would this be done in-game [graphically]?
The rifts themselves would be represented by a transparent graphic of some kind over the corresponding region in the field. (it would probably show under any creature summoned or moved there just like flooding).
When a player clicks on this card:
1) If there are no rifts present, all the open field slots on their side that have no rift would light up as viable targets.
2) If there is a rift present, all open fields slots their side that have no rift and all allied creatures would show up as viable targets.
Then,
If the player chooses an open field slot, a rift gets placed there.
If the player clicks on a creature, it gets moved to the nearest unoccupied rift. It then gains a stat bonus for as long as the rift remains open.
With 2 of these in play, you can easily open a rift and move a creature to it all in the same turn.
You could also use it as a simple stat buff by targeting a rift onto the slot that your next creature would get played to and then play the creature. It will get the buff for as long as the rift remains.
Finally, a decently done location-moving card...
But the way it works mentally calls to me as almost more of a 
theme then 
, persay...But that's partially just my gravity angst talking there...
In the spirit of filling in missing elemental niches, Time would be another good candidate... May need to change the name to "teseract" or something like that, but I think it still works out thematically.
The cool part would be that it would provide the
element with a way to provide stat buffs (which it currently lacks)
