Dread Presence. Whenever a swamp etb, choose one: draw 1 and lose 1 life or 2 dmg to ANY target and gain 2 life. Really, any target? So, I can kill planeswalkers and clear the board with swamps. There's a lot of strong land ramp in modern, enough to turn Dread into a draw engine to draw more ramp then kill your opponent.
Four mana is a lot to pay in modern without ramp, though. Plus, it's technically a 5 drop because you'll want to hit your land drop on the turn you play it. Urborg, Tomb of Yawgmoth + Fetchlands is a good way to net a lot of value from it, though.
It does have Turn 2 redundancy with Magnetic Theft, but if my testing with the Leyline of Abundance-Freed From the Real-Birds/Hierarch infinite combo is any indication, the London mulligan won't make it consistent enough, and your opponent will have a blocker or removal by Turn 2 surprisingly often.
You also need to take into account how there isn't any redundancy for the hammer itself. Sure, there are tutors available, but the combo simply doesn't work against most of the format once you pass the turn 2 surprise threshold. All of the equipment attachment cards are pretty lousy if drawn in multiples, without equipment, or slightly too late.
Salvager of Ruin costs 3 generic mana, is a 2/1, and can sacrifice itself to recur a permanent card to your hand that got ito the graveyard from the battlefield this turn. Worse Eternal Witness, I know....
It does have a few advantages over Eternal Witness, though. First of all, it's colorless, making it easier to cast, and, more importantly, an artifact. Its activated ability lets it synergize with Scrap Trawler to grab a 2 or less CMC artifact alongside an egg or a Mox Opal that turned into a Lotus Petal via the legendary rule. Having the ability be a sacrificing activated ability rather than an ETB also lets you loop two copies, potentially with the help of Semblance Anvil or some other form of cost reduction.
Four mana is a lot to pay in modern without ramp, though. Plus, it's technically a 5 drop because you'll want to hit your land drop on the turn you play it. Urborg, Tomb of Yawgmoth + Fetchlands is a good way to net a lot of value from it, though.
You also need to take into account how there isn't any redundancy for the hammer itself. Sure, there are tutors available, but the combo simply doesn't work against most of the format once you pass the turn 2 surprise threshold. All of the equipment attachment cards are pretty lousy if drawn in multiples, without equipment, or slightly too late.
It does have a few advantages over Eternal Witness, though. First of all, it's colorless, making it easier to cast, and, more importantly, an artifact. Its activated ability lets it synergize with Scrap Trawler to grab a 2 or less CMC artifact alongside an egg or a Mox Opal that turned into a Lotus Petal via the legendary rule. Having the ability be a sacrificing activated ability rather than an ETB also lets you loop two copies, potentially with the help of Semblance Anvil or some other form of cost reduction.