Vex and Action Order
The Rule
Vex appears in the Weapon Mastery section of the 2024 Player’s Handbook. Hit a creature with a Vex weapon and deal damage, and you have advantage on your next attack roll against that same creature before the end of your next turn. That’s the whole thing. No saving throw, no size restriction, no resource expenditure. Hit, deal damage, carry advantage forward.
The word that matters most is “have.” Not “may have.” Not “can choose to have.” You have advantage. It is not optional.
Common Misreadings
The mistake we see most often is treating Vex like a buff you bank and spend whenever it suits you. Players hit with a Vex weapon on their action, pocket the advantage, and then fire off a bonus action attack without thinking. The advantage burns on the smaller hit. If you’re a rogue running a rapier, that bonus action probably isn’t your sneak attack vehicle, which means you just fed your most valuable setup to the wrong attack.
The other misreading is treating Vex as transferable. It isn’t. The advantage is yours, against that creature, until the end of your next turn. Your fighter hitting with a Vex weapon does not set up the barbarian standing next to them, it sets up your fighter’s next swing.
Edge Cases
The Soulknife interaction is the one worth flagging. At level 3, Soulknife rogues manifest psychic blades that carry the Vex property as part of the feature itself, separate from their chosen Weapon Mastery properties. This means a Soulknife can have Vex running through the psychic blade and a different mastery property on their physical weapon simultaneously. The psychic blade’s Vex does not count against the Weapon Mastery properties they’ve selected. So you could, in theory, Vex on one attack and Topple on another in the same turn sequence, stacking the advantage from Vex into the Constitution saving throw trigger from Topple. The Topple DC doesn’t care about advantage on the attack roll itself, but advantage increases the odds you land the hit that forces the save in the first place. The chain is: Vex on a hit, carry advantage into the next attack, land that hit with better odds, force a Constitution save, prone a creature that is now disadvantaged on attack rolls while everyone within 5 feet swings at advantage. That is a lot of work happening off one Soulknife’s turn.
On the chaining question more broadly: Vex refreshes on a hit. If you hit with a Vex weapon at the end of your turn, you carry advantage into the next turn, hit again, and the advantage resets. The chain continues as long as you keep connecting. Against a single target you’re committed to dropping, a rogue with a rapier and sneak attack conditions already met is just a machine at this point. Hit, advantage, hit, advantage, with sneak attack riding along every time the conditions hold.
The “mandatory” clause creates a real decision point for anyone with Extra Attack or a bonus action attack. If your turn structure is bonus action first, then main action, you burn the bonus attack without advantage and arrive at your main action clean, ready to Vex into your next turn’s big swing. Reverse the order and you’re wasting the setup.
At the Table
The practical principle here is: plan your attack order before you roll. This sounds obvious and yet mid-combat, with everyone watching and the DM moving on, it’s easy to reach for the familiar sequence and lose the advantage before it pays off.
For rogues specifically, Vex is close to a sneak attack engine on its own. One of the conditions for sneak attack is having advantage on the attack roll. If you hit with a Vex weapon on your action, you enter your next turn with advantage already in hand, no ally adjacency required, no Help action needed. That is consistency that didn’t exist in 2014 5e, and it compounds over a full encounter in ways that raw damage comparisons don’t capture.
The one thing we want to flag for DMs: Vex does not care whether the creature you’re hitting has legendary resistance, legendary actions, or an immunity table longer than your arm. Advantage is advantage. Against high-AC targets where every attack roll matters, carrying advantage forward from turn to turn changes the feel of combat meaningfully. A rogue who used to pray for a flanking ally is now generating their own conditions. That is the design intent, and it works.
If you are building a character around Vex, the sequencing discipline is the skill. The weapon does its job. The question is whether you’re letting it.