Games like Guild's Requiem
Games like Guild's Requiem include Slay the Spire, Slay the Spire 2, 9 Kings, Griftlands, and Balatro. We matched them by the tags players give Guild's Requiem on Steam (Deckbuilding, RPG, Dark Fantasy, Card Battler, and Strategy): closest matches first, and among equally close ones the better-known games.

Slay the Spire
Shared: Deckbuilding · Card Battler · Strategy

Slay the Spire 2
Shared: Deckbuilding · Strategy · Card Battler

9 Kings
Shared: RPG · Strategy · Deckbuilding

Griftlands
Shared: Deckbuilding · Card Battler · RPG

Balatro
Shared: Deckbuilding · Strategy · Card Game

Roguebook
Shared: RPG · Deckbuilding · Strategy

Darkest Dungeon®
Shared: Dark Fantasy · RPG · Turn-Based Combat

Super Fantasy Kingdom
Shared: RPG · Strategy · Deckbuilding

Library Of Ruina
Shared: Deckbuilding · Strategy · Turn-Based Combat

Inscryption
Shared: Deckbuilding · Card Battler · Card Game

Monster Train
Shared: Deckbuilding · Card Battler · Roguelite

Die in the Dungeon
Shared: Deckbuilding · Strategy · Card Battler

Loop Hero
Shared: Deckbuilding · Roguelite · Dark Fantasy

Cross Blitz
Shared: Deckbuilding · RPG · Roguelite

The Last Spell
Shared: RPG · Strategy · Turn-Based Combat

Vampire Crawlers: The Turbo Wildcard from Vampire Survivors
Shared: Deckbuilding · Card Battler · Strategy

Tainted Grail: Conquest
Shared: Deckbuilding · Dark Fantasy · RPG

天外武林 (Traveler of Wuxia)
Shared: Deckbuilding · RPG · Card Battler

Deck of Ashes
Shared: RPG · Deckbuilding · Card Battler

Ratropolis
Shared: Deckbuilding · Card Battler · Strategy

Dicey Dungeons
Shared: Deckbuilding · Card Battler · Roguelite

HELLCARD
Shared: Card Battler · RPG · Deckbuilding

Dungeons & Degenerate Gamblers
Shared: Deckbuilding · Strategy · Card Battler

Deep Sky Derelicts
Shared: RPG · Deckbuilding · Card Battler