It is the ongoing nature of the life gain combined with its cheapness that make it so dangerous for aggressive decks
Outside of the Nexus of Fate win, the big problem with Darksteel Reactor in Historic is that it's basically a version of Simic Ascendancy that's harder to win with
Beyond this Temur shell, there are also Standard decks focused on resolving Reenact the Crime that get hosed by Rest in Peace
While the card itself isnt particularly powerful it lets you draw a card any time you cast an Aura, Equipment, or Vehicle spell its absolutely gorgeous
Its very easy to trigger, in other words, which makes Caretakers Talent a white Phyrexian Arena at a baseline
Osgir, the Reconstructor The first of two artifact heavy cards in a row, the penultimate scoring White card, the penultimate scoring Red card, the penultimate Commander 2021 deck leader, and arguably the most popular Commander in either set with 1194 decks built around him already over at EDHREC.com and growing