Mnemonic

Deep in the earth, a compass points to buried treasure. A ninja sneaks in, grabs all the money, and retires to ridiculous luxury—golden swords, silk masks, jewel-encrusted throwing stars, the works!
Additional thoughts
Picture the ninja underground using a compass to navigate tunnels of dirt toward a vault of money, then lounging in an absurdly lavish palace wearing silk. The over-the-top excess makes the image stick.
Quick recall
A ninja follows a compass through earth to money and retires in luxury.

Details

The keyword for 贅 is luxury. This kanji conveys the idea of extravagance, excess, and indulgence beyond what is necessary. It is often associated with lavish spending, superfluous possessions, or an opulent lifestyle that goes beyond basic needs. In Japanese, it frequently appears in expressions describing something as wasteful or unnecessarily elaborate.
On'yomi
ぜい、せい
Kun'yomi
いぼ

Used in vocab