Combo · ENGINE

Diana, Lunari × Undertitan — the only Predict in the pool that ends in a Reveal, so the deck can pay you back at every showdown

4 cards · mind + order · verified

Pieces

• Diana, Lunari ×1 UNL-079 · engine · mind

  When a showdown begins here, you may pay 1 Energy to [Predict], then reveal the top card of your Main Deck. If it's a spell, draw it. (To Predict, look at the top card of your Main Deck. You may recycle it.)

• Undertitan ×3 SFD-175 · payoff · order

  When you play me, give your other units +2 Might this turn. As I'm revealed from your deck, [Add] 2 Energy.

Payoff

Deck

• Diana is mono-Mind and Undertitan mono-Order, so 103.1.b.3 admits both to any Mind/Order identity. Grepping every legend line, that is exactly four: OGN-265 Herald of the Arcane, OGS-021 Lady of Luminosity - Starter, SFD-201 Chem-Baroness, UNL-199 Deceiver.
• Diana standing at a battlefield. Her trigger says 'here', and a unit is at one location, so only showdowns at HER battlefield count.

Prerequisites

• THE ENERGY IS A BASE COST PAID AT FINALIZATION, SO YOU MUST BANK IT BEFORE YOU MOVE. 383.3.b: a cost 'immediately following the "you may" ... that appears as the first part of the effect ... is treated as the base cost of the Triggered Ability', and 383.3.b.1: 'The cost must be paid in order to finalize the Triggered Ability to the Chain.' (383.3.b's second worked example, Insightful Investigator's 'You may pay 2 XP', is the contrast: not first in the effect, therefore paid on resolution.) 453 performs a Cleanup the moment the Move completes, 323.8 stages the Showdown and 323.12 begins it inside that same Cleanup, and 312.2 grants Priority at four times of which a Cleanup is none — so there is NO window between the move and the finalization. Add the Energy first; 167 keeps it, since the pool empties only at the start of a Main Phase and the end of a turn.
• IT FIRES ON THE OPPONENT'S TURN TOO, AND THERE THE ENERGY COSTS A RUNE. 461.3 and 464 ('Step 1: The Combat Showdown Step') / 464.2 make every Combat open with a Combat Showdown, so an attack into Diana's battlefield triggers her. Your pool is empty at the start of their turn (167), but 164.2.a gives every Basic Rune '[E]: [Reaction] — Add [1]' and 813.1.c.2 lets a Reaction ability be activated 'during Closed States on any player's turn' with 312.2.c / 312.2.d granting the Priority — so bank it in any earlier Closed State of their turn. The rune then stays exhausted until your own Awaken (315.1.b). With no such window, the 'may' is simply declined and 383.3.a.2 removes the trigger.
• #117's REASON FOR 'NOT ONCE PER TURN' IS WRONG; THE CONCLUSION SURVIVES ON A DIFFERENT RULE. The issue argued from showdowns being reopenable 'at different battlefields'. Diana's trigger says 'here'. On your own turn the count is near one anyway: 190.3.a.1 applies Contested only 'if that battlefield is not already Contested and that Unit's controller does not already control that battlefield', and 348.2.a hands you Control at the close. What makes it more than once per turn cycle is the opponent's attacks (461.3 / 464.2). And 323.14 caps the other direction: a Non-Combat Showdown that escalates BECOMES a Combat Showdown — it does not begin a second one, so no double trigger.
• UNDERTITAN ON TOP IS ONE ADD, NOT A STANDING TAX. 424.1.a.2 keeps a revealed card in the deck, which tempts a 'leave it on top and reveal it again next showdown' line. 315.4.b kills it: '1. The Turn Player draws 1', every turn, unconditionally — a card left on top is in your hand by your next Draw Phase. Each copy is worth at most one Add per trip to the top. 429.2 makes the Add resolve as soon as it is finalized; 167 decides how long it lives (spendable that Main Phase on your turn, Reactions only on theirs).
• IT IS TWO LOOKS, NOT A SEARCH, AND THAT IS THE WHOLE CLAIM. Predict first: if the top card is a spell, leave it and the Reveal draws it; if not, recycle it to the BOTTOM (416.1.a / 416.5) and the Reveal shows a fresh card. So one Energy buys two chances, the second informed by the first — which is what separates this from the blind reveals it shares a payoff with. Per #117's finding 4 nothing in this lens turns that probability into a certainty: no card in the pool searches the Main Deck for a named card.
• OVERLAP, DECLARED. reksai-undertitan-reveal (SFD-170 + 3x SFD-175) and void-rush-undertitan-accelerate (SFD-188 + SFD-175 + SFD-029 + SFD-018) already use Undertitan. Both are blind reveals inside a Void shell on your own attack; this is an informed reveal inside Mind/Order that also fires on the opponent's turn. Same payoff card, different shells.
• SAFE IN A DECK-EMPTY SHELL: 436.4.a (Predicting with too few cards does not Burn Out) and 431.1.c (looking or revealing in excess does not Burn Out) both apply; only the mandatory 315.4.b draw can burn you, and that is not this card.
• 370.1.b.1 NAMES THIS CARD IN ITS OWN WORKED EXAMPLE AND WAS UNCITED HERE (upgrade 2026-09-12; a debt two separate lanes flagged). An *"as you look at or reveal me"* clause is a REPLACEMENT EFFECT, not a Triggered Ability: 370.1.b.1 - *"In the case of Replacement Effects that describe a game action to occur `as` an event occurs, the described event is replaced by that same event plus the game action being performed"* - and 371.2 is what makes its *"you may"* legal. Three consequences a trigger would not buy: there is **no Chain Item**, so no window exists between the look and the body arriving; it is **immune to every trigger multiplier in the pool** (`OGN-236 Karthus` doubles Deathknells, `UNL-087 Blue Sentinel` and `UNL-029 Red Brambleback` double Hold and Conquer triggers, and none of them can see a replacement); and 431.1.c keeps the look itself free of Burn Out.
• WHY AN ABILITY ON A CARD NOBODY HAS PLAYED WORKS AT ALL, WHICH THIS FAMILY CITED FOR NEITHER (upgrade 2026-09-12, #187 batch 15). Every entry in the Undertitan/Nocturne family cites 370.1.b.1, which says what KIND of ability it is and nothing about why it is active in the Main Deck. Three paragraphs answer that: **365.1 is the DEFAULT that would kill the family** - *"Passive Abilities of Permanents are typically only active while on the Board"*; **366.1 is the OVERRIDE** - *"Passive Abilities of cards in zones that are outside of the Board will self-describe their context"* - which was cited by TWO entries out of 762, neither of them here; and **368.1** - *"Passive Abilities can be Replacement Effects"* - had ZERO citations anywhere and is the hinge, because it is what makes 366.1 rather than 385.1 the applicable block. This project carries 385.1 and 385.2, the TRIGGERED-outside-the-board pair, at 16 and 42 citations and had never had the passive counterpart, so a reader reaches for 385 and gets the wrong block. **424.1.a.2** completes it - cards remain in the zone they are being Revealed from, with Riot naming the top of the Main Deck - which is why the self-described context is satisfied at the instant the passive fires.
• 370.3 IS THE NARROWEST AND MOST ON-POINT PARAGRAPH FOR THIS CARD AND IT WAS MISSING FROM THE WHOLE FAMILY (self-audit upgrade 2026-09-12, #187 batch 20). The earlier pass prescribed 365.1, 366.1, 368.1 and 424.1.a.2, which are about PASSIVE ABILITIES IN GENERAL. **370.3 is about REPLACEMENT EFFECTS AND ZONES SPECIFICALLY**: *"If a Game Object has a Replacement Effect that is active in a specific zone, it is evaluated and subsequently applied if it enters that zone before an event occurs that it could replace."* Measured on 2026-09-12 it was cited by **exactly ONE entry in 762** and by none of this family. 366.1 says a passive outside the board self-describes its context; 370.3 says a replacement effect can be ACTIVE IN A ZONE and is applied if the object entered that zone first - and for a card sitting in the Main Deck since the game began that timing half is free, **which is exactly why it is easy to leave out** and why its worked example is the case where the half BITES.
• 204.3.a IS THE FIRST AND CLEANER SOURCE FOR THIS, AND IT CARRIES THE WORKED EXAMPLE: "When Costs within Instructions appear as the first part of the effect in triggered abilities, the cost is taken to be the base cost of the triggered ability. It must be paid to finalize the triggered ability", with Riot's example being Overzealous Fan - "When I defend, you may kill me to move an attacking unit to its base" - and the note that "in order to finalize the ability to the chain, its controller must kill Overzealous Fan". 383.3.b says the same thing later in the book. The companion is 204.3.b: a cost appearing in a SPELL, in an ACTIVATED ability, or in a LATER part of a trigger's effect is paid on resolution instead, which is the 205 "pay X. If you do, Y" family and the reason the two look alike on the card and behave differently on the chain.

Steps

1. Play Diana, Lunari (3 Energy) and get her to a battlefield.
2. BEFORE moving anything that will open a showdown there, put 1 Energy in your Rune Pool — 383.3.b makes it the trigger's base cost and 383.3.b.1 makes it payable only at finalization, with no Priority window inside the Cleanup that opens the showdown (312.2, 453, 323.12).
3. Move into the battlefield (or let the opponent attack into it). 190.3.a applies Contested; 323.8 stages the Showdown; 323.12 or, when their units are there, 461.3 / 464.2 open it as a Combat Showdown. Either way a showdown BEGINS at Diana's location.
4. Her trigger finalizes for 1 Energy. Predict 1 (436.1): look at the top card. If it is a spell, leave it. If it is Undertitan, leave it. Otherwise recycle it to the bottom (416.1.a, 416.5).
5. Reveal the top card (424.1). If it is a spell, draw it. If it is Undertitan, 385.2 lets its ability work from the Main Deck and 429.2 Adds 2 Energy at once — net +1 Energy on the activation.

Per iteration

one free look plus one revealed card per showdown at Diana's battlefield, for 1 Energy: a free draw whenever the revealed card is a spell, and +2 Energy (net +1) whenever it is an Undertitan

How it ends

engine only — capped by how many showdowns open at Diana's own battlefield (roughly one per player's turn), and each Undertitan is worth one Add before 315.4.b draws it into your hand

Sources

Published elsewhere

• Riot gallery card text (data/corpus_flat.txt, 2026-09-04, errata applied) 2026-09-04
• Riftbound Core Rules, Last Updated 2026-07-16 (data/Riftbound-Core-Rules-2026-07-16.txt) 2026-07-16
• Deck-manipulation lens — issue #117 (GitHub) 2026-09-06

Walked here, in this project

• Hand walk 2026-09-06 2026-09-06 record

Walked against Core Rules 2026-07-16

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