mtg collect evidence cards Can you use excess evidence? : r/mtg exile cards with total mana value 6 or greater from your graveyard.) Target creature you control gets +2/+0 until end of turn Magic The Gathering - Murders

Ghost Town gives you a way to bring down your land count on demand without giving up any permanent resources

Void Rend

Libera tu lado ms malvado y demuestra que el mal siempre gana

Of these two, the Azorius variant is far more popular indicating that it's better to enchant your creatures with Curious Obsession, Arcane Flight, Staggering Insight than to eke out value with Hateful Eidolon and Dead Weight

Efficiency can be determined simply by the reward you receive at certain mana costs (Counterspell and Cancel do the same thing, but Counterspell costs less), the total payoff you receive from a single card (Hull Breach and Decimate are both good cards, but Decimate usually covers much more ground), or the payoff you receive in conjunction with other cards (Anointed Procession makes other token production cards completely absurd if unchecked, which is usually better than adding one more card that simply makes tokens like Spectral Procession in a token strategy)

There's nothing better than combining two cards to produce an absurdly powerful reaction which ends the game in short order