Games like Underlight
Games like Underlight include Neverwinter, The Elder Scrolls Online - Standard Edition, Guild Wars 2®, Albion Online, and Blue Protocol: Star Resonance. We matched them by the tags players give Underlight on Steam (1990's, MMORPG, Massively Multiplayer, Retro, and Fantasy): closest matches first, and among equally close ones the better-known games.

Neverwinter
Shared: MMORPG · Massively Multiplayer · RPG

The Elder Scrolls Online - Standard Edition
Shared: MMORPG · RPG · Fantasy

Guild Wars 2®
Shared: MMORPG · RPG · Massively Multiplayer

Albion Online
Shared: MMORPG · Massively Multiplayer · Free to Play

Blue Protocol: Star Resonance
Shared: MMORPG · Massively Multiplayer · RPG

Destiny 2
Shared: MMORPG · Free to Play · PvE

FINAL FANTASY XIV Online
Shared: MMORPG · Massively Multiplayer · RPG

Where Winds Meet
Shared: Free to Play · Fantasy · Massively Multiplayer

Warframe
Shared: Free to Play · Massively Multiplayer · RPG

Star Trek Online
Shared: Massively Multiplayer · MMORPG · Free to Play

Trove
Shared: MMORPG · Free to Play · Fantasy

Path of Exile
Shared: MMORPG · Free to Play · Action RPG

The Quinfall
Shared: Massively Multiplayer · MMORPG · RPG

Karos
Shared: Massively Multiplayer · MMORPG · RPG

Pantheon: Rise of the Fallen
Shared: MMORPG · Massively Multiplayer · RPG

ATLYSS
Shared: RPG · Action RPG · Adventure

SpiritVale
Shared: MMORPG · Massively Multiplayer · RPG

Diablo® IV
Shared: RPG · Action RPG · MMORPG