Perhaps the best way to keep an odd number of cards in hand are abilities that let you draw
The Evoke Elementals like Solitude
However, you can consider playing fewer than four copies of a card if: It gets worse in multiples (such as legendary creatures) It's only useful against certain matchups It's a win condition, and your control deck will have time to dig through the deck and find it You're stuck choosing between two cards which have equally strong, similar, but slightly different effects (you could play two of each) It's a slightly worse version of a card you have four copies of already, and you're including it because you want even more of that effect
Her two abilities are Trance which lets you send the top two cards from your deck to the graveyard (called milling) and in return, Terra gains Flying, making her much more difficult to block
On paper this looks like a two to four mana investment for something that doesn't even ramp you for following turns unless you didn't otherwise have lands to make
Finally, complete your collection with the Pikachu pack