Perhaps the best way to keep an odd number of cards in hand are abilities that let you draw
Doing so can ensure that both you and your buyers are happy with each sale
Muxus, Goblin Grandee Muxus, Goblin Grandee absolutely crushed some Constructed formats upon release
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
It can fetch answers or combo pieces like Rest in Peace or Phyrexian Unlife, so you can adjust your plan based on what the game demands
But even treating this as a 4-mana 3/2 that draws you a card sounds really good, and you can obviously divide up when you cast the two halves to make it feel even better and if you always have the mana available when it dies, it will just keep coming back When it has a big enough friend around, it is going to be an intimidating attacker on any board and that alone is enough for the Ruiner to be relevant almost all game long