Design an uncommon that fits in an instant/sorcery deck.
Let's start the voting!
[Cardname]
Artifact Creature - [Creature Type]
Whenever you cast an instant or a sorcery spell, put a +1/+1 counter on ~
[2/2]
Empty Spellbook Artifact (U)
, sacrifice ~: Draw a card, then draw another card for each spell you cast this turn.
When I graduated, my teacher gave me such a tome. That book is the one I taught you from. I have nothing left to teach you. Today you receive your book.
Totemic Staff –
Artifact (U) Oblation—Whenever you cast an instant or sorcery spell, you may sacrifice Totemic Staff. If you do, cast a copy of that spell without paying its mana cost. You may choose new targets for the copy.
Archmage's Staff ArtifactWhenever you cast an instant or sorcery spell, you may have ~ become an X/X Snake creature until end of turn, where x is that spell's converted mana cost.
Focus Stone
Artifact (U)Whenever you cast an instant or sorcery spell, the next instant or sorcery spell that shares a color with it you cast this turn costs
less to cast.
Electromancer's Stone
Artifact (U)
Instant and sorcery spells you cast cost
less to cast.
Sacrifice Electromancer's Stone: Put at target instant or sorcery card chosen at random from your graveyard on top of your library.
Lurking Defenses Artifact (U)
Whenever you cast an instant or sorcery spell, you may have target noncreature artifact you control become a 2/2 artifact creature until end of turn.
Scavengers learn quickly to put their torches out around inactive automatons, lest the appearance of daybreak end their long slumber. I vote for Cato.