A Solar Eclipse is a Hardmode event that occurs rarely after at least one Mechanical Boss has been defeated. A Solar Eclipse has a 1/25 (4%) chance of occurring on any particular day (for comparison, the Blood Moon has a 1/10, or 10% chance, each night).
During a Solar Eclipse, unique and difficult enemies spawn at very high rates, even near NPCs. The event lasts for one entire day, from sunrise to sunset, regardless of the number of enemies that have been killed. The moon is visible in front of the sun, causing the ambient light level to drop to near-nighttime levels.
A Solar Eclipse is announced at the beginning of a day with the message, "A solar eclipse is happening!" The event only affects the surface layer, and can be avoided by burrowing well into the underground layer or below.
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| From Reaper:
| From the Cyborg:
- It is possible for other events to occur at the same time as a Solar Eclipse, such as a Goblin Invasion. Other events may cancel Solar Eclipse enemy spawns.
- Swamp Things seem to be the most common Solar Eclipse enemies to spawn, followed by Frankensteins, Reapers, and Vampires, with Eyezor being the least common.
- A Solar Eclipse can occur the day before or after a Blood Moon. One will not affect the chances of the other following, and the same event can follow the next day or night as well.
- Every enemy but the Reapers and Vampires use standard Fighter AI, and even share the same jump range as basic Zombies.
- Unlike a blood moon, it has only its own enemies, where blood moons have most regular enemies ( with the exception of the groom and clowns). The only exception is in corruption, Crimson, and the Ocean.
- Like the Blood Moon, the effects of Water Candles and Battle Potions stack with the event's spawn rate, increasing the chances for rare drops.
- Enemies that spawn during a Solar Eclipse share the theme of classic 20th century horror films.
- The type of Solar Eclipse experienced is an annular solar eclipse.
- When loading a world with a Solar Eclipse in progress, the sun that rises and sets on the loading screen is also in its eclipsed state.
- 1.2.2: NPCs will now shelter in their housings during a solar eclipse.
- 126.96.36.199: No longer requires defeating Plantera to happen, only defeating a Mechanical Boss.
- 188.8.131.52.1: Now only occurs after defeating Plantera. 
- Slightly increased the chance for an eclipse to happen, from 1/30 to 1/25, but they will now only happen after killing a Mechanical Boss.
- Eclipses are no longer persistent between worlds.
- 1.2: Introduced.
| Game mechanics|
|Attack Speed • Breath meter • Buffs • By hand • Consumable • Crafting station • Critical hit • Damage • Data IDs • Day/Night • Death • Debuffs • Defense • Difficulty • Environment • Event • Fall Damage • Game controls • Ghost • Health • Inventory • Knockback • Lighting mode • Mana • Map Size • Minimap • Minions • Modifier • Moon • Music • NPC drops • NPC Spawning • Placement • Player stats • Rarity • Spawn • Storage • Use time • Value • Velocity|