Other awesome cards with the mechanic are Bonfire of the Damned and Entreat the Angels
I like this with a few genres
One such of these spells was Viscerid Drone, which at the cost of two for one against your favor could take out virtually any creature in the format
But what it does, as I see it, is simply adding a ton of synergy and consistency to the decks that play it
For example, if a token enters the battlefield as a copy of Boon-Bringer Valkyrie, that backup ability can have another creature gain its keywords until end of turn
Sometimes you make decks that are too efficient, brutal, or broken, while other times, your initial deck idea is stone cold against a certain popular archetype or lacks the power to hang with other casual decks