Quote from ashtonkutcher »There are plenty of cards in straight UR that care about cards in the grave, including Snapcaster, Reveler, and Lavamancer. And others that care about spells being cast, like Swiftspear, Thing, and Pyromancer. It's close to impossible to have this conversation without an actual list as a blueprint though, so if you can point me to a UR Delver list with a recent finish we'll be able to delve into the topic constructively. If not, my point stands that cantrips (and especially sorcery-speed ones) synergize on multiple levels in this archetype.
According to my definition, whether or not it plays green cards, UR Delver is indeed a thresh deck. Perhaps yours is different, but after reading that definition, do you disagree that it fits UR Delver?
Someone already linked to one a little bit earlier. In fact, it's the only one with any results worth noting.
It really seems to agree with the basic idea. That getting instants and sorceries into the grave is useful, but that once you get a delver or pyromancer onto the field, you'd much rather play at instant speed than sorcery in order to constantly threaten your opponent with counterspells, hence why the only sorcery is Serum Visions, and the other cycles have the same benefit that Opt does. It's less of a burden to use since you can just use them on the turns that you held up (Or bluffed holding up, often the effect can be the same) countermagic to slow your opponent down and ended up not needing to use it (Thought Scour and Heiroglyphic Illumination) while Heiroglyphic Illumination also has a much higher ceiling than Sleight of Hand, becoming a full card advantage spell in grindy matchups.
The only on cast trigger is Young Pyromancer. Lavamancer and Serpent find having a card in the graveyard useful, but they're also anti-synergy with each other and most likely one's sided out when the other is brought in, meaning that at most 6 creatures care about the graveyard at any one point in time, but in the case of Sleight of Hand... are you really unable to find a better card to flashback than Sleight of Hand? The only spell that Sleight of Hand puts into your graveyard for Snapcaster Mage is Sleight of Hand, when Thought Scour is not only instant, but has a chance of putting spells that you actually want to flashback into the pool. All Snapcaster needs is a single instant or sorcery, and Sleight of Hand would be one of the lowest priority flashback targets.
Sleight of Hand might have some synergy with the deck, but it's so minor that it's certainly not good enough to justify running the abysmal Sleight of Hand, and I really don't see how you could claim that sorcery speed cantrips synergise especially well in a deck type that runs counterspells given that instant speed cantrips mean that you can leave mana open on your turn to deter opponents with the threat of countermagic and then still make use of your mana even when they play around it, making instant speed all the more valuable and mitigating the tempo loss.
If you wanted to make it work, you'd probably want to run it in a deck with far more on cast synergies, like full on Kiln Fiend and Prowess style creatures, and even then you'd probably rather run different cantrips like Slip Through Space to make sure that those grounded attackers can actually connect.
Additionally, if you're going to go with that that definition, Sleight of Hand is also a terrible fit. "Often trades card advantage for speed" and "disrupts opponents with noncreature spells" are heavily at odds with Sleight of Hand. Cantrips are one of the biggest cases of trading speed for card advantage, as they tend to have much less powerful effects than other spells of their mana cost due to the fact that they're a 0 card advantage instead of a -1, and a part of Delver's disruption suite is counterspells, which require the ability to hold mana open on the opponent's turn, but have the drawback of potentially backfiring and wasting the held open mana if the opponent doesn't play anything worth countering and you have nothing at instant speed that you can play end of turn. As a card selection, sorcery speed cantrip, Sleight of Hand is an abysmal fit for that description.