The Old Man is an NPC whose primary function is to summon Skeletron. He can be found at the Dungeon's entrance. When spoken to at night, the Old Man will give the player the option to "詛咒", which summons Skeletron. When spoken to during the day, the Old Man will tell the player to return at night. He will also judge players with 300 maximum health (15 hearts) or less, or 10 defense or less as unworthy but still allows them to summon Skeletron.
The Dungeon can be entered without defeating Skeletron, but traveling deeper than ground level within it (below zero depth) will spawn Dungeon Guardians that will most likely kill the player on contact (see Guide:Dungeon Guardian strategies).
- The Old Man can be hurt with lava, Dart Traps, which cause normal damage and debuff effects, and explosives. He will also take damage from a rolling Boulder and Suffocation like all other NPCs. However, enemies cannot hurt him, and he does not defend himself against them ( unlike other NPCs), although he will still run away from them.
- If the Old Man dies or the player fails to defeat Skeletron, the Old Man will respawn at the Dungeon entrance the following day.
When the player has 300 or less max health or 10 or less defense:
When the player has more than 300 max health and more than 10 defense:
- Other NPCs will "interact" with the Old Man and engage in conversations.
- He is the only NPC that will not defend himself and is not damaged by enemies. He also cannot be drowned.
- He is one of only two friendly NPCs that does not have a map icon, the other being the 骷髏商人. However, he does appear as a white dot similar to an enemy.
- Upon summoning Skeletron, the Old Man dies, which makes it seem as if he turns into Skeletron. One possibility is that he is possessed by Skeletron and simply wishes to die before he causes more harm to others.
- 老人的 怪物圖鑑條目：「This hapless Old Man carries the burden of a heavy curse. It's said at night he transforms into a horrific demon which guards the Dungeon.」
- 電腦版 188.8.131.52：The Old Man's Bestiary entry will now fill itself out upon the death of Skeletron if it somehow doesn't get filled out due to other circumstances.
- 電腦版 184.108.40.206：外觀更新。
- 電腦版 1.0.5：The Old Man now warns players before transforming into Skeletron at night.