Cast a Magnet Merchant Shopping Guide

The merchant is Cast a Magnet’s timed convenience shop: luck potions, mutation vials, and other session tools that turn a normal casting block into a rare hunt. Sweg Magnets’ Roblox incremental still runs on the same loop — cast, clear the reel minigame, sell heavy finds for Cash, upgrade Real Power, Rope Length, and Luck, then display keepers at your base — but the merchant decides whether that Cash becomes a sharp buff or a regret receipt. This guide covers when to check stock, how to compare 2x versus 4x versus mutation vials, and the Cash floor rules that keep upgrades on schedule.

Pair every merchant visit with luck and potions for buff math and with item values so you know which bag contents fund the buy.

What the merchant actually sells

Community feature lists for Cast a Magnet consistently expose merchant / auto-buy targets around:

• 2x Luck Potions (shorter and longer duration variants)
• 4x Luck Potions (same duration split, stronger multiplier)
• Mutation vials — Sandy, Charged, Phased, Gold, Rainbow, Diamond
• Occasional QoL or session tools that rotate with UPD patches

Exact prices and SKUs can change after an 🚨UPD banner. Always read the live tooltip. Treat this page as shopping discipline, not a frozen price sheet. When Sweg Magnets retunes stock, skim updates before assuming last week’s “always buy 4x” rule still holds.

Video guide

Golden rule: shop after you sell

Open the merchant after a sell pass, not mid-cast and not while the bag is still full of unsorted junk.

1. Finish the current cast / reel cleanly.
2. Triage the bag — display keepers, mark duplicates, sell junk.
3. Note your real Cash number.
4. Glance at the next Real Power / Rope Length / Luck breakpoint from upgrades.
5. Then open merchant stock and decide.

Shopping before you sell lies to you. A half-full bag looks poor; a sold bag reveals whether you can afford a 4x without skipping the rope rank that unlocks better water.

Wait for good market windows

Not every merchant refresh is worth your time. Good windows look like:

• You already planned a focused rare hunt this session.
• Weather / event banners are live or about to flip (see mutations and weather).
• Perfect cast timing feels sharp — you will actually use the timer.
• Display slots have room for keepers (display base).
• Bounties or index goals need rare or mutated tags.

Bad windows:

• You are five minutes from logging off.
• Cash sits one rank below a critical rope or power buy.
• Inventory is clogged and you will Sell All under panic.
• You still have unspent community Luck Potions from joining the official Roblox group.

Waiting is a skill. Skipping a mediocre 2x to bank Cash for tomorrow’s weather + 4x combo often prints more rares than drinking every vial the merchant waves at you.

2x vs 4x vs mutation vials

2x Luck Potion

Best when you want a short, honest rare bump without emptying the wallet. Use 2x for:

• Warm-up hunts after a perfect cast drill
• Filling a bounty that needs “any rare” rather than a specific mutation
• Sessions where you might get interrupted

4x Luck Potion

Best when the whole session is dedicated. Preconditions:

• Rope Length already reaches the water you care about
• Real Power can secure heavy results
• You will stay focused for the full tooltip duration
• Keepers have somewhere to go besides Sell All

Drinking 4x and then AFK-selling commons is the most expensive merchant mistake in Cast a Magnet.

Mutation vials

Sandy, Charged, Phased, Gold, Rainbow, and Diamond vials tag pulls with special variants. Buy them when you intend to keep results for index or display — not when you need raw Cash. If your finger is hovering over Sell All, you are in a Cash session; skip mutation stock. Deep dive: mutations and weather.

Quick compare table

Stock	Buy when…	Skip when…
2x Luck	Short focused block, solid timing	You already hold free community potions
4x Luck	Long hunt + weather/bounty align	Cash below next power/rope breakpoint
Mutation vial	Index / display hunt planned	You will liquidate everything for upgrades
Duplicate SKU	Never — bank the Cash	Inventory already holds the same vial

Never empty Cash below upgrade breakpoints

Merchant stock is a timing tool, not a rebirth substitute and not a code channel. Protect the three permanent stats:

1. Leave enough Cash for the next Real Power rank if heavies still contest.
2. Leave enough for Rope Length if a new shoreline feels short.
3. Only then spend overflow on luck potions or mutation vials.
4. Permanent Luck ranks still beat impulse vials when you cast for hours between merchant visits.

A simple floor: after buying, you should still afford at least one meaningful upgrade if the next bag is average. If the purchase leaves you at zero with a weak magnet sheet, you overbought.

Session templates that respect the merchant

Cash grind (merchant closed)

Perfect cast → sell junk → buy power/rope → repeat. Ignore flashy vials. Goal: raise the floor.

Merchant rare hunt

1. Clear inventory and free a display slot.
2. Sell junk; note Cash.
3. Confirm weather / bounties.
4. Buy 2x or 4x only if the budget clears the upgrade floor.
5. Optionally add a mutation vial for index holes.
6. Cast with discipline until the timer ends.
7. Display mutations and true rares; sell the rest; revisit upgrades.

Index fill with merchant help

Stack a luck potion with the mutation vial that matches your missing variant. Stop when the timer ends — starting a second paid vial while tired wastes Cash and casts.

Codes, free potions, and merchant overlap

As of November 2026 there are no confirmed promo codes for Cast a Magnet. Track the empty-but-ready list on codes and redeem flow on how to redeem when a string appears. Until then, free value still exists: join the official Roblox community for the advertised 3 free Luck Potions, claim them on the same account you play, and bank those vials before buying merchant duplicates.

Merchant stock is not a substitute for those community gifts. Spend Cash on gaps your free vials do not cover.

Auto-buy scripts versus manual discipline

Automation hubs expose Auto Buy Merchant style toggles because the shop matters. Blind auto-buy is how Cash disappears into vanity stock. If you study scripts or Plak auto farm, whitelist only progression SKUs and keep a Cash reserve rule that mirrors this guide. Manual players should copy the same whitelist mentally: power/rope first, then luck buffs that match a real hunt.

Common merchant mistakes

• Checking stock with a full unsorted bag
• Buying 4x with no display space
• Drinking paid potions while free community vials sit unused
• Emptying Cash the rank before a rope breakpoint
• Treating every refresh as mandatory
• Ignoring item values and selling a unique mutation to afford a duplicate 2x

Related pages

• Upgrades — protect breakpoints before you shop
• Luck and Potions — permanent Luck versus timed buffs
• Mutations and Weather — when vials and events stack
• Display Base — park keepers before the buff ends
• Item Values — fund buys without dumping trophies
• Codes — verified promos when they exist

Master the sell-then-shop rhythm and the merchant stops being a Cash sink. It becomes the button you press when Cast a Magnet’s shoreline is already warm, the bag is clean, and the next cast block deserves a real multiplier.