Combo · ENGINE

Kennen grants a SECOND [Flow] cost to a spell that already prints one — 829.1.c.3 makes it a choice, and the expensive half is the only thing that reaches the Library

3 cards · chaos · verified

Pieces

• Kennen, Storm of Shuriken ×1 VEN-113 · engine · chaos

  When you play me, [Burn 2]. (Put the top 2 cards of your Main Deck into your trash.) When I conquer, give a spell in your trash [Flow] equal to its cost this turn. (You may play it from your trash for its Flow cost. Then banish it.)

• Twilight Step ×1 VEN-105 · enabler · chaos

  Move a unit with 3 Might or less. [Flow] 4 Energy + 1 Chaos Power (You may play this from your trash for its Flow cost. Then banish it.)

• Forgotten Library ×1 UNL-211 · battlefield

  While you control this battlefield, when you play a spell, if you spent 4 Energy or more, [Predict]. (Look at the top card of your Main Deck. You may recycle it.)

Payoff

Deck

• Legend domains cover Chaos — Kennen and Twilight Step are both mono-Chaos and the Forgotten Library is colorless, so any Chaos legend runs the whole line (103.1.b.1).

Prerequisites

• THE ENTRY IS 829.1.c.3 AND NOTHING ELSE: 'If a spell has multiple instances of the Flow keyword with different costs, its controller may choose which cost to apply as they play it.' The obvious reading of Kennen — that his grant REPLACES the printed Flow, so an expensive-Flow spell becomes cheap — is wrong in a way that matters: the two instances COEXIST and you pick one at the moment you play it. Fifteen spells in the pool print [Flow] (VEN-003, VEN-012, VEN-031, VEN-049, VEN-051, VEN-081, VEN-100, VEN-105, VEN-116, VEN-127, VEN-140, VEN-144, VEN-148, VEN-154, VEN-156, measured over data/corpus_flat.txt on 2026-09-12) and Kennen is the pool's only Flow granter, so he is the only route to two instances on one card.
• WHY THE CHOICE IS WORTH ANYTHING: THE POOL'S PRINTED FLOW COSTS ARE A TAX. Measured over all fifteen on 2026-09-12: nine are strictly more expensive than the spell's own base cost (VEN-003, VEN-031, VEN-105, VEN-127, VEN-140, VEN-148, VEN-154, VEN-156, and VEN-144 in Power), four are equal (VEN-012, VEN-049, VEN-081, VEN-100, VEN-116) and one is cheaper in Energy while adding a rune (VEN-051). Kennen's grant is 'equal to its cost', i.e. the base cost, so for nine of the fifteen his instance is the CHEAP one. Twilight Step is the clean case inside his own domain: 2 Energy + 1 Chaos granted against 4 Energy + 1 Chaos printed.
• AND THE EXPENSIVE INSTANCE IS THE ONLY ONE THAT REACHES THE LIBRARY. 829.1.c.1 — 'The cost is an alternate cost that replaces the base cost of the spell to be paid during finalization' — is what makes the Flow cost the thing that actually leaves the Rune Pool (166.2, 203.1), and the Forgotten Library reads what you SPENT, not what the card costs. Choose the printed 4 Energy and the Library predicts; choose Kennen's 2 and it does not. One card in the trash covers the tempo turn and the Predict turn, and the choice is made after you have seen the board.
• STARGAZER IS ANTI-SYNERGIC WITH THE LIBRARY HALF, WHICH kennen-stargazer-arena-flow DOES NOT SAY. VEN-098 Stargazer reads 'Spells with [Flow] you play from your trash cost 2 Energy less, to a minimum of 1 Energy' — a discount, not an option, so it applies to whichever instance you chose. Twilight Step's printed 4 becomes 2 and Kennen's granted 2 becomes 1, and NEITHER reaches the Library's threshold of 4. The two Kennen lines in this catalogue want opposite second cards: kennen-stargazer-arena-flow wants the discount, this one refuses it.
• THE FLOW PLAY IS STILL A MAIN PHASE PLAY, AND IT IS ONE PER COPY. 829.1.b.2: 'Playing a spell for its Flow cost does not change the timing at which it can be played, nor any permissions for the spell aside from the zone from which it can be played' — Twilight Step carries neither [Action] nor [Reaction], so the grant arriving on a Conquer in your Main Phase is fine and the spell is played later in that same Main Phase, inside Kennen's 'this turn'. 829.1.b.1 makes the banish a delayed replacement effect, so each copy is re-flowed exactly once and 103.2.b caps the name at three.
• THE BATTLEFIELD IS NOT GUARANTEED AND STARTS SWITCHED OFF. A deck may not carry two of a battlefield of the same name (Core Rules 103.4.c, Tournament Rules 402.1), it is randomly selected 1 of 3 in a Duel (485.5) and in Skirmish (487.5) and selected in a Match (486.5), and 190.1 starts it uncontrolled — 190.6.d then ignores every instruction in it until you take it, because the card says 'you'. The Library is colorless, so the opponent may bring it too.
• 436.4.a KEEPS THE PREDICT SAFE IN AN EMPTY-DECK SHELL: 'The Player will not perform a Burn Out as a result of Predicting with too few cards in their deck.' Kennen's own [Burn 2] is 431.1.b milling and DOES burn past the deck, so the two halves of this card pull in opposite directions and the Burn is the half to be careful with.

Steps

1. Play Kennen, Storm of Shuriken (3 Energy + 1 Chaos Power). His play trigger burns the top 2 of your Main Deck into your trash.
2. Hold or take the Forgotten Library. 190.1 starts it uncontrolled and 190.6.d ignores 'while you control this battlefield' until you control it.
3. Get a Twilight Step into the trash — cast it normally for 2 Energy + 1 Chaos, or let Kennen's [Burn 2] put it there.
4. Conquer with Kennen. His trigger gives that Twilight Step [Flow] equal to its cost: 2 Energy + 1 Chaos Power, this turn. The card now carries two Flow instances with different costs, its printed 4 Energy + 1 Chaos and Kennen's 2 Energy + 1 Chaos.
5. Still in that Main Phase, play it from the trash and CHOOSE which cost to apply (829.1.c.3). Take Kennen's 2 when you only want the move; take the printed 4 when you want the Forgotten Library's [Predict], because 829.1.c.1 makes whichever you chose the amount that leaves the Rune Pool.
6. The spell is banished as it leaves the chain (829.1.b.1). Next Conquer, a different spell in the trash.

How it ends

engine — one spell out of the trash per Conquer at a cost you choose between two, and a free [Predict] on the turns you pay the higher one; no loop, and each copy is re-flowed once

Sources

Published elsewhere

• Riftbound Core Rules, Last Updated 2026-07-16 (data/Riftbound-Core-Rules-2026-07-16.txt), 829.1.c.3 and 829.1.c.1 2026-07-16
• Riftbound Core Rules, Last Updated 2026-07-16 (data/Riftbound-Core-Rules-2026-07-16.txt), 829.1.b, 829.1.b.1 and 829.1.b.2 2026-07-16
• Riftbound Core Rules, Last Updated 2026-07-16 (data/Riftbound-Core-Rules-2026-07-16.txt), 166.2, 203.1, 190.6.d and 436.4.a 2026-07-16
• Card text, data/corpus_flat.txt (built from Riot's gallery content API by scripts/build-cards.mjs) 2026-09-12

Walked here, in this project

• Hand walk 2026-09-12 (docs/phase0/walks/2026-09-07-uncited-subrules-500-899.md, section 34), issue #191 2026-09-12 record

Walked against Core Rules 2026-07-16

Match a deck list against the whole catalogue