Goblin Electromancer's effect reduces only generic mana in the spell's total cost.
05-10-2018
wotc
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
14-03-2017
wotc
Two Goblin Electromancers will make instant and sorcery spells you cast cost {2} less to cast, and so on.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.