Things that show the location of other objects

• Spelunker Potion — Treasure and ore.
• Hunter Potion — Enemies.
• Biome Sight Potion — Corrupted tiles.
• Metal Detector
• Spelunker Glowstick and Spelunker Flare
• Magic Lantern — Treasure.
• Suspicious Looking Tentacle — NPCs, enemies, treasure, and ores. (Expert mode-exclusive, post-Moon Lord)
• Map viewers — 3rd party programs.