Soul Mate

Plainswalkers can be casted as instants and
can block/attack like creatures (x/x equil to there loyalty).
Abilities cost {x} instead of loyalty to activate.
Tap Plainswalker-creature after you trigger an
ability.
“The most powerful magic is not of the Plainswalkers
but of two souls in love and absolute unity”
-Ral Zarek, Izzet League champion and Planeswalker