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the Undertitan comes ready, and they kill Rek'Sai

Issue #311 (a slice of #200), 2026-10-07. Constructed, Duel (485). Rules version 2026-07-16. Card text verbatim from data/corpus_flat.txt; rules pasted from data/Riftbound-Core-Rules-2026-07-16.txt. Read the unopposed clock for the baseline this is measured against.

Subject: void-rush-undertitan-accelerate, the Fury/Order ENGINE in which SFD-188 Void Rush reveals SFD-175 Undertitan, the reveal adds two Energy toward the Undertitan's own discounted play, and SFD-029 Rek'Sai, Breacher gives it [Accelerate], so a 5-Might body enters ready and gives your other units +2 Might. The entry is right about the rules: 369.1 names the Undertitan as a replacement effect, and the banishment zone is not a hand. Walked as a game, Void Rush finds an Undertitan on T3 a little more than one cast in four, and then it takes the opponent's battlefield from a seven-Might garrison. The price is three runes off the board. And the +2 and the ready are only worth anything in an attack, which puts Rek'Sai in the fight, and the defender kills her first. In the walk the line ran once. Two things the entry has wrong change the deck. Void Rush is a Rek'Sai Signature card, so the only legend that can run it is SFD-187 Void Burrower. And that legend reveals the top two on every conquer, which is the same line for one Power less, with no spell to counter. What breaks the spell route is OGN-045 Defy, one rune, before anything is revealed.

Why this line. scripts/sequence-pick.mjs --unplayed, re-run on 2026-10-07 at b2bea92, reads 771 entries, 262 with forced-ordering language, 102 in the queue and 61 of them with no play, unchanged from the issue. The pick is by global rank, skipping entries that already have a play: this entry is rank 40 (a hit on before), second in the list, because rank 39 already has a play. The other entry of this slice is rank 38, played in the Musicians take B at six and hold it at three.

1. Needs

LegendSFD-187 Void Burrower, and no other: Void Rush carries the Rek'Sai tag and is a Signature card (103.2.d.2)
ChampionSFD-029 Rek'Sai, Breacher as the Chosen Champion, so she starts in the Champion Zone and is never a draw
FirstRek'Sai on the board, and SFD-018 Void Hatchling if you have one
ThenVoid Rush in hand, and five runes to tap with three to recycle, two of them Order

The card text the play turns on:

2. Your order: reveal, add, play, ready

The legend comes first, because the spell names it. 103.2.d.2: "All of the Signature cards must have the Champion tag that corresponds to the Champion Legend of the deck." Void Rush is tagged Rek'Sai and marked Signature in data/cards.json, and Void Burrower is the pool's only Rek'Sai legend. 103.2.d.1 caps the count: "Regardless of name, a deck may only contain a sum total of 3 Signature cards." The three Void Rush are the whole allowance. Rek'Sai, Breacher is a champion unit with the legend's tag, so she can be the Chosen Champion (103.2.a.2) and start the game outside the deck, 419.1.a: "By default, a player can only Play cards from their hand or their Chosen Champion zone." So the deck the reveals sample is 39 cards, and the enabler is in no draw at all.

The Add is in the pool before the play. 369.1 works this card: "Undertitan is a unit that reads in part “As I’m revealed from your deck, [Add] [2].” This is a replacement effect that alters the execution of any Game Effect that reveals Undertitan from your deck." The reveal and the Add are one event. The card stays on top until something moves it, 424.1.a.2: "Cards remain in the zone they are being Revealed from." Then Void Rush banishes it and plays it, and the two Energy pay part of the cost.

The price. Void Rush is two Energy and one Power. The Undertitan is E6 + 1 Order Power, reduced by two Energy. Rek'Sai's grant is 805.1.a: "As you play me, you may pay [1][C] as an additional cost. If you do, I enter ready." 805.1.a.1 fixes the Power: "the Power portion of the Accelerate cost can be paid only with a Power that matches one of the domains of the unit", which for the Undertitan is Order. 805.6: "It does not enter exhausted and then become ready." That is seven Energy and three Power, less the Add's two: five runes tapped and three recycled, as the entry says. Going first on T3 you have six. Three are left after the line, and T4 opens on five runes where the curve has eight.

The ready and the +2 point at one thing. The +2 lasts this turn, and the ready is worth something only this turn, because your next Awaken readies the Undertitan anyway (315.1.b). The one use of both, on the turn they arrive, is a move into a battlefield you do not control. Rek'Sai is the best body to send with it: three, plus two, plus her [Assault], is six.

3. Their order: B, then A

Calm/Mind with VEN-145 Curator of the Sands, idle in the walk because nothing costs seven. Stalwart Poro takes B on their T2 and Sunlit Guardian joins it. Both have [Shield], so B defends at three and four, seven, and the Guardian has [Tank]. Ravenbloom Student goes to their base, and all five runes are spent. On their T3 they cannot take B back, so the Student walks into A, trades with your Hatchling, and leaves A with nobody, 466.5.b: "If there are no Units remaining here controlled by any player, the Battlefield becomes Uncontrolled." That costs you the Hold on T4.

4. The turns, going first

Fury/Order against Calm/Mind. Your rune deck is six Fury and six Order, channelled Fury and Order each turn, so T3's six runes are three of each. That covers Void Rush's Power whichever domain it names. This list runs three Hatchlings, two more than the entry declares; both counts are priced below.

turn    runes   your turn                                                 points
T1      2       Void Hatchling (E2) to base                               0
their T1        Stalwart Poro to base, with the 485.7 extra rune.
T2      4       Hatchling walks to A, Conquer: +1. Void Burrower: the     1
                Hatchling looks at the top card and keeps it; Blazing
                Scorcher and Scrapyard Champion are revealed, five
                Energy each, so both are recycled. Rek'Sai (E3) from
                the Champion Zone to base, one idle.
their T2        Poro walks to B, Conquer. Sunlit Guardian (E3) to B,
                Ravenbloom Student (E2) to base. All five runes spent.
                B defends at seven.
T3      6       Hold A: +1. Void Rush (E2 + 1 Power). The Hatchling       3
                recycles Noxus Saboteur off the top; Undertitan and
                Void Drone are revealed. Add 2. The Undertitan
                (E4 + 1 Order) with [Accelerate] (E1 + 1 Order) enters
                ready, and your other units get +2. Draw the Drone.
                Five tapped, three recycled: three runes left. Rek'Sai
                and the Undertitan walk to B: eleven against seven.
                Both defenders die; they kill Rek'Sai. Conquer: +1.
their T3        No Hold. The Student walks to A: two against the
                Hatchling's two, both die, and A is uncontrolled.
                Lecturing Yordle (E3) and Eager Apprentice (E3) to
                base, one idle.
T4      5       Hold B: +1. Void Drone (E3) and Pouty Poro (E2) to B.     4
their T4        Yordle and Apprentice walk into A. Conquer.

Their points: 1 on T2, still 1 after T3, 2 on T4. The opponent was never idle. They took B with a garrison of seven and, when they could not take it back, cost you A instead.

The T3 move is one action, 144.3: "This is treated as one game action performed on multiple Units." Rek'Sai is six and the Undertitan five. You assign first: the Guardian has [Tank] and takes its lethal four first, the Poro three, and four are spare. Their seven can kill one of the two: the Undertitan's lethal is five and Rek'Sai's is six. Either kill leaves one body at B, and they choose Rek'Sai. She is the [Accelerate] for every later Void Rush, and the only Breacher on the board. The Undertitan holds B.

The legend readied at your T3 Awaken (315.1.b), so the Conquer at B offers a second reveal. It is declined. One rune is open, and an Undertitan revealed now would add two Energy and still cost E6 + 1 Power through the legend, so it would go to the bottom unplayed.

What the line bought. After their T3 the score is 3 to 1. Without the Undertitan, Rek'Sai alone is four against seven, B stays theirs and they Hold it on their T3: 2 to 2. So the line swung two points and left a 5-Might body on their battlefield. It cost three runes of growth, Void Rush, and Rek'Sai, and until another Breacher is drawn, the next Void Rush plays its unit exhausted.

How often this T3 happens. On T3 the deck has 30 unknown cards on top (39, less seven drawn, less the two T2 recycled to the bottom). With all three Undertitans among them, Void Rush finds one 19.3% of the time. The Hatchling's look and recycle raise it to 28.0%, and that is the number this walk used. Getting there needs a Void Rush in the first seven cards (45.7%) and a Hatchling in the first five for T1: 34.5% with three, 12.8% with the entry's one, without a mulligan. A Void Rush that misses still plays one of the two cards, two Energy cheaper and ready if it is a unit, and draws the other. But without the Undertitan's five Might, its two Energy and its +2, it does not make eleven.

5. Breaks to

The spell route breaks to OGN-045 Defy (Calm, E1 + 1 Power: one rune, tapped for the Energy and then recycled for the Power), held on their T2 in place of the Student and cast on Void Rush, which costs two Energy and one Power. 425.1.a: "A card or ability that is Countered does nothing and is cleared from the chain." Nothing is revealed, so there is no Add and no Undertitan. 425.1.c: "Countering does not refund any costs paid to play a card, activate an ability, or trigger an ability." You lose one of your three Signature cards, two runes tapped and one recycled. Rek'Sai alone is four against seven, so the T3 swing does not happen, and their T3 Holds B: 2 to 2. They paid one rune. Fury/Order prints no counterspell, so there is no reply in the identity.

The reply is the route that is not a spell. Void Burrower's reveal is a triggered ability on a Conquer, and Defy counters spells. Through the legend the Undertitan costs its full E6 + 1 Order Power. The Add pays two of that, and [Accelerate] adds one Energy and one Order: five runes tapped and two recycled, one Power less than the spell route, with no card spent. It needs a Conquer with those runes still open, which means walking in before you spend.

6. Verdict

Right, a T3 swing on a little more than one Void Rush in four, and it runs once. The rules reading is right. The Add is a replacement effect, it lands before the play, and Rek'Sai's grant reaches a card played from banishment. The play adds three prices. The line takes three runes off the board, so T4 is five runes where the curve has eight. The ready body and the +2 only pay in an attack, and Rek'Sai has to attack beside the Undertitan to make it large, so the defender kills her and the next Void Rush has no [Accelerate]. And the spell is a main-phase spell that the cheapest counter in the pool takes for one rune before anything is revealed. The better engine is the legend the deck is forced to run.

7. Not verified

I did not deal the channel order; two Order runes among six from six Fury and six Order fail in 37 of 924 deals (4.0%). The corpus prints Void Rush's Power as P1 without its domain; three Fury and three Order on T3 cover either. I did not walk the legend route as a game, a T3 that misses, SFD-170 Rek'Sai, Swarm Queen as the Chosen Champion, the mulligan, or 2v2. The defender's choice is theirs: had they killed the Undertitan, Rek'Sai would hold B at three on their T3 against a Student at two, and they would still spend that turn on A.

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