The Battlefield

Cloud Key

$1.31

Krark-Clan Ironworks

$21.73

Myr Retriever

$2.48

Scrap Trawler

$1.50

AI DraftFeb 26, 2026

Cloud Key + Krark-Clan Ironworks + Myr Retriever + Scrap Trawler

Overview

With Cloud Key choosing artifact (Cloud Key), Krark-Clan Ironworks (KCI), Scrap Trawler and Myr Retriever you get a repeating loop that produces net + {C}

each full cycle and therefore infinite colorless mana; Cloud Key reduces only the generic portion of artifact spells' costs (Ruling [2021-03-19]) and KCI's sacrifice is an activated ability that produces {C}

when you sacrifice an artifact as its cost (). Scrap Trawler can return an artifact card with lesser mana value than the artifact that went to the graveyard (Ruling [2017-02-09]) and Myr Retriever can return another artifact card when it dies (Ruling [2020-08-07]).

Step 1

Set Cloud Key to artifact so artifact spells you cast cost {1}

less to cast (Ruling [2021-03-19]).

Step 2

Have Krark-Clan Ironworks and Scrap Trawler on the battlefield and Myr Retriever in your graveyard (this is one valid starting setup); alternately you can have Retriever on the battlefield and Trawler in the graveyard — the loop requires one of them in the graveyard to start.

Step 3

Activate Krark-Clan Ironworks, sacrificing Scrap Trawler as the activation’s cost: the sacrifice moves Trawler to your graveyard and causes Trawler’s triggered ability to trigger (Scrap Trawler’s 'dies' or 'another artifact is put into a graveyard' trigger) (see Ruling [2017-02-09]).

Step 4

When Trawler’s triggered ability resolves, return Myr Retriever from your graveyard to your hand (Retriever’s mana value 2 is less than Trawler’s mana value 3, satisfying Scrap Trawler’s return requirement per Ruling [2017-02-09]).

Step 5

Paying the activation cost completed, the KCI activation will produce {C}

when it resolves; you now have that colorless mana available to spend ().

Step 6

Cast Myr Retriever from your hand. Cloud Key reduces Retriever’s generic cost by {1}

, so its cost is {1}

instead of {2}

(Ruling [2021-03-19]). Pay {1}

of the

you gained from KCI; that leaves {C}

in your mana pool.

Step 7

Activate Krark-Clan Ironworks again, sacrificing Myr Retriever as the activation’s cost. Myr Retriever’s death trigger will target Scrap Trawler in your graveyard (Ruling [2020-08-07]) and will return it to your hand when the trigger resolves.

Step 8

When KCI’s activation resolves it produces another {C}

; combined with the {C}

left from earlier you now have {C}

in your pool. Cast Scrap Trawler from your hand for its reduced cost {2}

(Cloud Key reduces its {3}

), leaving {C}

in the pool.

Step 9

You are back to the starting battlefield position (Scrap Trawler on the battlefield, Myr Retriever in graveyard) plus a net {C}

in your mana pool. Repeat the sequence to generate another {C}

each cycle; because each full cycle increases your colorless mana by {C}

, you can repeat to produce arbitrarily large amounts of colorless mana (Ruling [2021-03-19]; Ruling [2017-02-09]; Ruling [2020-08-07]; ).

Resolution

If Cloud Key is set to 'artifact' and you have KCI + Scrap Trawler + Myr Retriever with one of the two artifacts initially in the graveyard, you can loop by alternately sacrificing the creature on the battlefield to KCI and recasting the other: each full loop (sacrifice Trawler → return Retriever → cast Retriever → sacrifice Retriever → return Trawler → cast Trawler) nets {C}

of colorless mana, so repeating the loop generates infinite colorless mana (Ruling [2021-03-19]; Ruling [2017-02-09]; Ruling [2020-08-07]; ).

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