Games like Down the Drain
Games like Down the Drain include Cult of the Lamb, The Binding of Isaac: Rebirth, Hades II, GRIS, and Hades. We matched them by the tags players give Down the Drain on Steam (Action Roguelike, Dungeon Crawler, Cute, Female Protagonist, and Hand-drawn): closest matches first, and among equally close ones the better-known games.

Cult of the Lamb
Shared: Action Roguelike · Cute · Dungeon Crawler

The Binding of Isaac: Rebirth
Shared: Action Roguelike · Dungeon Crawler · Singleplayer

Hades II
Shared: Action Roguelike · Female Protagonist · Dungeon Crawler

GRIS
Shared: Female Protagonist · Hand-drawn · Singleplayer

Hades
Shared: Action Roguelike · Dungeon Crawler · Singleplayer

Vampire Survivors
Shared: Action Roguelike · 2D · Singleplayer

Carto
Shared: Cute · Hand-drawn · Female Protagonist

Slime Rancher 2
Shared: Cute · Singleplayer · Colorful

Muse Dash
Shared: Cute · Female Protagonist · Singleplayer

Slime Rancher
Shared: Cute · Singleplayer · Adventure

Enter the Gungeon
Shared: Action Roguelike · Dungeon Crawler · 2D

Skul: The Hero Slayer
Shared: Action Roguelike · 2D · Singleplayer

Hollow Knight: Silksong
Shared: 2D · Singleplayer · Female Protagonist

Dead Cells
Shared: Action Roguelike · 2D · Adventure

UnderMine
Shared: Action Roguelike · Dungeon Crawler · Singleplayer

Dungreed
Shared: Action Roguelike · Dungeon Crawler · 2D

Melatonin
Shared: Cute · Hand-drawn · 2D

Bing in Wonderland
Shared: Cute · Hand-drawn · Action Roguelike

Florence
Shared: Cute · Female Protagonist · Singleplayer

Hollow Knight
Shared: 2D · Singleplayer · Hand-drawn

Have a Nice Death
Shared: Action Roguelike · 2D · Singleplayer

SULFUR
Shared: Action Roguelike · Dungeon Crawler · Singleplayer

The Binding of Isaac
Shared: Action Roguelike · Indie · Singleplayer

Dreamscaper
Shared: Action Roguelike · Dungeon Crawler · Female Protagonist