Games like The Last Portal
Games like The Last Portal include Bloons TD 6, Orcs Must Die! 3, Age of Darkness: Final Stand, Kingdom Rush - Tower Defense, and Thronefall. We matched them by the tags players give The Last Portal on Steam (Strategy, Tower Defense, 3D, Fantasy, and Combat): closest matches first, and among equally close ones the better-known games.

Bloons TD 6
Shared: Strategy · Tower Defense · Singleplayer

Orcs Must Die! 3
Shared: Tower Defense · Strategy · PvE

Age of Darkness: Final Stand
Shared: Tower Defense · Strategy · 3D

Kingdom Rush - Tower Defense
Shared: Strategy · Tower Defense · Fantasy

Thronefall
Shared: Strategy · Tower Defense · 3D

Age of Mythology: Retold
Shared: Strategy · 3D · Fantasy

Plants vs. Zombies GOTY Edition
Shared: Tower Defense · Strategy · Singleplayer

Kingdom Rush Frontiers - Tower Defense
Shared: Strategy · Tower Defense · Fantasy

Kingdom Rush 5: Alliance TD
Shared: Strategy · Tower Defense · Fantasy

Rogue Tower
Shared: Strategy · Tower Defense · 3D

Element TD 2 - Tower Defense
Shared: Tower Defense · Strategy · Fantasy

Dungeon Defenders
Shared: Tower Defense · Strategy · Singleplayer

Kingdom Two Crowns
Shared: Tower Defense · Strategy · Singleplayer

Orcs Must Die!
Shared: Tower Defense · Strategy · Fantasy

Legion TD 2 - Multiplayer Tower Defense
Shared: Tower Defense · Strategy · PvE

Emberward
Shared: Tower Defense · Strategy · 3D

Kingdom Rush Vengeance - Tower Defense
Shared: Strategy · Tower Defense · Singleplayer

Orcs Must Die! Deathtrap
Shared: Tower Defense · Strategy · Fantasy

Kingdom Rush Origins - Tower Defense
Shared: Strategy · Tower Defense · Singleplayer

Total War: WARHAMMER II
Shared: Strategy · Fantasy · Singleplayer

Crimson Desert Enhanced
Shared: Singleplayer · Combat · Fantasy

GemCraft - Chasing Shadows
Shared: Strategy · Tower Defense · Fantasy

Artisan TD
Shared: Strategy · Tower Defense · Fantasy

Tiny Tactics
Shared: Strategy · Tower Defense · 3D