Aura of Silence: A speedbump and removal. Very powerful, but has to be committed to the board to have an effect, making it vulnerable to opposing enchantment removal. Also competes with
Disenchant and various other options for space, and comes down on turn 3 rather than
turn 2, making it worse against
Standstill.
Boil: Control decks in Premodern don't typically play enough Islands to justify running this, even though it's instant speed and can therefore be sequenced around counterspells better than Armageddon. Some combo-control decks do play many basic Islands, though, and this is good against those archetypes.
Conversion: Can ruin a Sligh player's day, but probably not much more than Sphere of Law will. Doesn't deal with an on-board Sulfuric Vortex.
Disenchant: Instant speed removal for stuff like Cursed Scroll, Scroll Rack, Mox Diamond, Tangle Wire, Masticore (sometimes), Winter Orb, Powder Keg, Black Vise, Zombie Infestation, Fires of Yavimaya, Phyrexian Arena, Recurring Nightmare, Aluren...
Enlightened Tutor: A versatile, powerful tutor.
Gilded Light: Primarily an anti-Storm card, but has incidental utility against some other combo decks. Now that Yawgmoth's Bargain is banned, playing an anti-graveyard card in this slot is probably correct, though.
Humility: Since we play very few creatures, this is an option to absolutely nerf whole archetypes. Can be used as a pseudo-wrath, a mass Needle effect, or both at the same time. Of course, we already play anywhere from two to eight mass removal effects, not counting virtual copies from Burning Wish. And we can't save our creatures from this with Astral Slide as we can with our wraths.
Karma: Problems with Monoblack Control? Not anymore! (Just watch out for Nevinyrral's Disk).
Light of Day: The hoser of choice against Sui, Psychatog, and other black-heavy decks.
Null Rod: Wrecks certain metas and decks, and often does so permanently, unlike artifact removal. A card with a low floor and a high ceiling.
Pyroblast / Red Elemental Blast: Beats about a thousand cards in Magic's most powerful color. Split between PB and REB to preserve equity against Meddling Mage.
Radiant's Dragoons: Does an okay Siege Rhino impression against aggro, and is backbreaking for all aggressive decks when combined with Astral Slide. It is four mana plus Echo, clunky, and pretty bad in non-aggro matchups, though.
Runes of Protection: In this deck, these are upgraded versions of Circles of Protection, since they can cycle. The white mana activation cost is usually not as relevant as the cycling, so I would recommend running these if you're going to run a protection effect. Meta calls.
Seal of Cleansing: An onboard version of Disenchant, with obvious applications against Standstill decks. Given the prevalence of UW Landstill and Stiflenought in Premodern, this is a worthwile inclusion into many lists.
Shattering Pulse: It can't be grabbed with Burning Wish but it can be used multiple times... for six mana a pop. That's a pretty steep cost, but repeatable removal is pretty good. As with Null Rod, the value of this card goes up with the number of artifact decks at your LGS.
Sphere of Law: Turns Lightning Bolt into Hornet Sting and Sulfuric Vortex into draft chaff. Run at least two.
Teroh's Faithful: A worse Radiant's Dragoons, without echo. You're not playing Dragoons for their amazing on-board stats, but this might be better on occasion.
Warmth: A cheaper version of Sphere of Law, except against Sulfuric Vortex, which is in just about every red aggro deck in Premodern. Don't try to dodge Vortex - play Sphere.
Tormod's Crypt: Can be activated at instant speed and costs zero mana. Has to be deployed on the board, though, making it vulnerable in many cases. And you can't Wish for it. If you're running into Reanimator, Pandleburst, Breakfast, or Goblin Welder a lot, playing several of these is a good idea.