So this is what came out after I tried to build around the cards Isochron Scepter, Young Pyromancer and Guttersnipe.
The deck idea is simple. You either shoot damage with Guttersnipe, Isochron Scepter+ Lightning Bolt/Price of Progress or you overrun your opponent with 1/1 tokens provided by Young Pyromancer.
The average mana costs are pretty low in order to be able to play as much as possible each turn. I also included a lot card draw/card cycling action to ensure you will never run out of spells to cast.
To maximize the efficiency of Isochron Scepter, I included only one spell (twice) that can't be used by it (of course the aim was to include no sorcery spells at all, yet the card advantage Ideas Unbound provides is just a necessity) .
My personal favorite combinations might be Isochron Scepter+ Manamorphose followed by Isochron Scepter+ Price of Progress. Manamorphose itself is already one of the best cards you could possibly play in Guttersnipe/Young Pyromancer decks, but if used with Isochron Scepter, you get one of the best card draw and manafixing engines there is in Magic. The reason why Price of Progress+ Isochron Scepter isn't my first choice: because it doesn't work against every deck type. However, the damage output of this combi each turn is just insane against decks with non-basic lands (which by the way is the reason why there are no non-basic lands in my deck).
As of now, I am not sure whether or not I should replace Unsummon with Boomerang. Boomerang certainly has the better effect, but the mana costs of UU are a real bother. I also don't like playing Terramorphic Expanse, but I simply cannot afford Scalding Tarn yet.
Please feel free to play with this deck and/or give your opinions.You might even upvote it in case you like this deck.
(Side note: yes, tapping Isochron Scepter to cast a copy of the exiled spell triggers Young Pyromancer and Guttersnipe, since it clearly says "you may cast the copy". Just a question that came up a few times while testing this deck.)
