The Vampire tribe might have what it takes to present a threat as one of the aggressive decks of the Pioneer format. We can play a few choice synergies, some aggressive 1-drop creatures, and a smattering of the best cheap disruption in the format.
Orzhov Vampires Decklist (Pioneer)
4 Knight of the Ebon Legion 4 Vampire of the Dire Moon 4 Indulgent Aristocrat 4 Skymarcher Aspirant 4 Legion's Landing/Adanto, the First Fort 4 Cruel Celebrant 4 Sorin, Imperious Bloodlord 4 Champion of Dusk 4 Thoughtseize 2 Fatal Push 4 Godless Shrine 4 Concealed Courtyard 4 Caves of Koilos 4 Isolated Chapel 4 Swamp (339) 2 Plains (331)
Sorin, Imperious Bloodlord is really the reason to try to build a deck like this. For an aggressive creature-based deck, it gives us a ton of reach to close out the game when our opponent stabilizes. It also gives us then nut draw of curving out 1-drops on the first two turns, then dropping Sorin into Champion of Dusk to draw four cards. Champion of Dusk is castable at five mana when we don't have this draw, especially with Adanto, the First Fort.
Indulgent Aristocrat completes our list of vampire-based synergies. We have plenty of 1-drops so that we can go wide quickly in order to take advantage of its pump effect. We can get cheap fodder to repeatedly sacrifice if we are able to transform Legion's Landing. We also have several creatures with powerful keywords such as lifelink that benefit from growing larger than their base stats.
We're starting with Cruel Celebrant in this list instead of Legion Lieutenant, though that could be a mistake. The ability to gain some reach, especially when this is drawn in multiples, seems good when we have Indulgent Aristocrat as an additional sacrifice outlet to complement Sorin.
Thoughtseize and Fatal Push are some of the absolute premium interaction in the format. Fatal Push is better in this deck than most, since we have several ways to trigger revolt. If we end up wanting to include higher numbers of Fatal Push, we could consider running Fabled Passage.
Is this deck good enough for Pioneer? Time will tell, but efficient 1-drop creatures supplemented by some synergies and disruption is an easy way to pick up wins, so we'll give this deck a shot against the wide open metagame!