Sea Monster of Theseus

2017 Mega-Tin Mega Pack, Yu-Gi-Oh!, MP17-EN231, Secret Rare

Printing: 1st Edition, Near Mint

$1.44

TCGplayer market price (an average of recent sales)

As of Oct 27 (today).

Buy on TCGplayer Search on eBay

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Price trend

Oct 19 $2.74 → Oct 26, 2026 $1.44 −47.4%

$2.74$2.00$2.50$1.44

Oct 19, 2026Oct 21, 2026Oct 22, 2026Oct 23, 2026Oct 26, 2026

Sep 26 $9.07 → Oct 26, 2026 $1.44 −84.1%

$9.07$4.00$6.00$8.00$1.44

Sep 26, 2026Oct 6, 2026Oct 11, 2026Oct 16, 2026Oct 26, 2026

Jul 28 $20.45 → Oct 26, 2026 $1.44 −93.0%

$21.18$5.00$10.00$15.00$1.44

Jul 28, 2026Aug 27, 2026Sep 11, 2026Sep 26, 2026Oct 26, 2026

Oct 26, 2025 $1.20 → Oct 26, 2026 $1.44 +20.0%

$26.71$1.17low$10.00$20.00$1.44

Oct 26, 2025Feb 24, 2026Apr 26, 2026Jun 26, 2026Oct 26, 2026

Feb 8, 2024 $2.32 → Oct 26, 2026 $1.44 −37.9%

$26.71$0.50low$10.00$20.00$1.44

Feb 8, 2024Jan 3, 2025Jun 17, 2025Nov 29, 2025Oct 26, 2026

Vs its set

Over the 90 days to Oct 26, 2026: this card −93.0%; the median other card in 2017 Mega-Tin Mega Pack +5.6% (238 other cards, each at its tracked printing).

Market details

Sold vs asking

Recent sales (TCGplayer market price)$1.44

Sellers asking (median listing)$4.80

0$4.80

Sellers ask 3.3× the recent sale price.

Asking figure from TCGplayer listings, as of Oct 27.

Record

Price history Feb 8, 2024 to Oct 26, 2026

Highest$26.71May 5, 2026 only

Lowest$0.50Jul 19, 2025 only

Vs highest95% below $26.71

Price changes, last 30 days

Date	Price	Change
Oct 19	$3.89 → $2.74	−29.6%	Show on chart
Oct 21	$2.74 → $2.40	−12.4%	Show on chart
Oct 22	$2.40 → $2.11	−12.1%	Show on chart
Oct 23	$2.11 → $1.64	−22.3%	Show on chart
Oct 25	$1.64 → $1.48	−9.8%	Show on chart
Oct 26	$1.48 → $1.44	−2.7%	Show on chart