Thats because Reya Dawnbringer, in addition to a not too shabby 4/6 Power and Toughness (though you may be expecting more for such an expensive card), can bring one creature per turn back from your graveyard, returning it straight to your battlefield
Enrage triggers even if the creature dies from the damage dealt
Our reason for making this change is based on metagame data and play rates of companion decks across all formats, and on player feedback on repetitive gameplay patterns, Wizards said in an update to banned and restricted cards
But after Pro Tour Aetherdrift, a version of this deck that runs red is ramping up in popularity
There are any number of brutal combos you can execute here, including using Spine of Ish Sah as removal and damage each turn, or using Scrap Trawlers effect in tandem with Foundry Inspector and Sculpting Steel to infinitely loop artifacts in and out of your graveyard