During a Party most NPCs, and even some enemies, can be seen wearing a Party Hat, will display unique dialog when spoken to and some will sell unique items.

While a Party is going on, different colored balloons are floating all around the sky in the background.

The event will always end on dusk.

The Lantern Night is an event that occurs in celebration of the player's victory over a boss or invasion for the first time. The Party Girl will sell the Release Lantern and the player will have a flat +0.3 increase to their Luck stat.

During such a night many lanterns can be seen rising up into the sky in the background.

Rain can occur in any surface biome, changing the theme music and background, as well as dimming the lighting. Goldfish start to walk on land, and most NPCs will have unique dialog. Once the rain has ended, the effects fade away and the affected biome returns to normal. Rain in a Snow biome becomes a blizzard.

Rain always lasts 24 in-game hours.

In addition to regular surface enemies, the following enemies will spawn:

Waterleaf plants, found in the Desert, will bloom during rain. Furthermore, NPCs will remain in their houses regardless of the Day/Night Cycle and all players are granted a +20% boost to their Fishing Power.

A Sandstorm only affects players in a Desert. During a Sandstorm, visibility is somewhat decreased, the Mighty Wind debuff will be inflicted, pushing all creatures afflicted with it in the direction of the wind, and particles will appear in the dusty yellow background. Sandstorms can also occur in Hallowed, Corrupted, and Crimson Deserts.

In addition to regular Desert enemies, the following enemies will spawn:

A Windy Day results in increased cloud cover and stronger wind effects. If a Windy Day happens at the same time as a Rain, the result is a Thunderstorm.

In addition to regular Forest surface enemies, the following enemies will spawn:

A Thunderstorm is a rare weather event where both the Rain and Windy Day events combine. During a Thunderstorm, lightning will occasionally flash on the screen and the lighting will dim even further than the Rain. The wind also blows much more ferociously than normal. All effects from the Rain event also occur during a Thunderstorm.

A Meteor Shower is an event during which falling stars appear all throughout the sky in the background. Meteor Showers greatly increase the spawn rate of Fallen Stars, and causes Enchanted Nightcrawlers to spawn, resulting in easily obtainable bait.

The Blood Moon is an event that lasts an entire night. During this event, the spawn rate of enemies and the maximum amount of enemies that can be on the screen at any time is increased. Enemies will also spawn near NPCs and most become capable of opening doors with a couple hits, even though they normally can't. The event can be skipped using an Enchanted Sundial.

During the event, fishing power is increased, and several new dangerous enemies can spawn when the player fishes.

In addition to regular surface enemies, the following enemies will spawn:

Deathweed blooms during a Blood Moon.

Some regular Critters will turn Corrupt/Crimson when a Blood Moon rises.

All water in the world (aside from the Ocean, Fish Bowls, and Water Fountains), including rain, gain a blood red color, similar to the Crimson's natural water color.

The Goblin Army is an event where unique Goblin enemies spawn in waves. When a Goblin Army is approaching, one of the two following status messages will appear: "A goblin army is approaching from the west!" / "A goblin army is approaching from the east!"

During the event, five ( six during Hardmode) different types of goblins will spawn:

Although they do not appear in the Goblin Army, Goblin Scouts can be found rarely on the outer thirds of the map. They drop Tattered Cloth which is used to craft the Goblin Battle Standard, the summoning item for this event.

The event is completed after a certain number of goblins have been defeated. Afterwards, the Goblin Tinkerer NPC can be found underground.

Slime Rain is an event where different variations of slimes constantly fall from the sky until the day or night is over. If the player kills 150 slimes before the event ends naturally, King Slime will spawn, 75 slimes if King Slime was previously defeated.

Many types of slimes spawn, including:

After King Slime is defeated, the event will stop immediately.

The Old One's Army is a unique Dungeon Defenders 2 crossover event that can be initiated after rescuing the Tavernkeep, who can be found on any layer after defeating the Eater of Worlds/Brain of Cthulhu. The objective is to protect the Eternia Crystal from waves of enemies seeking to destroy it. If the Crystal is destroyed by enemies, the event terminates. If it is kept safe until all waves are cleared, the event is won.

Both the Crystal and its Stand are purchased from the Tavernkeep NPC for coins. Players are inflicted with the Creative Shock debuff for the duration of the event, which prevents the removal or placement of blocks during the entire event within a certain range.

Each wave becomes progressively more difficult. If triggered before any Mechanical Bosses have been defeated, the event consists of 5 waves. If triggered after at least one Mechanical Boss is defeated, the event consists of 7 waves. Once Golem has been defeated, the event becomes even more difficult with the boss Betsy spawning in the final wave. Only one Betsy will spawn during each invasion and defeating it will complete the event. The event also contains 2 mini-bosses, the Ogre and the Dark Mage.

The following enemies are exclusive to the event:

The Torch God is a mini-event that happens when 101 torches accumulate in close proximity underground. The placed torches begin launching small fireballs at the player, extinguishing themselves in the process. The fireballs deal 40 / 80 / 120 damage, and they travel in straight lines through blocks. They can also spawn from torches located off-screen.

While the event is active, the player is inflicted with the Blackout debuff, significantly reducing the player's light vision.

When all torches are extinguished, the event ends. After a brief period, the torches reignite, and if 101 or more torches have been activated, the Torch God's Favor drops near the torches. The player can not challenge the event again once the player has a Torch God's Favor either in their inventory or consumed, and must create another character to do so. A player that has not consumed a Torch God's Favor can continuously challenge and complete the event and obtain more Torch God's Favors, as long as they do not have one in their inventory.

The Frost Legion is an event that functions similarly to the Goblin Army, but it requires an item to start the event, which is only attainable in Hardmode. During Christmas, enemies will drop presents. If the world is in Hardmode, these presents have a 7.69*1/13 (7.69%) chance of containing a Snow Globe, which is used to spawn the Frost Legion.

During the event, three different types of unique snowmen will spawn:

All of the snowmen drop Snow Blocks, technically granting the player a way to obtain infinite amounts of Snow.

The event is completed after a certain number of snowmen have been defeated. Afterward, the Santa Claus NPC will spawn during Christmas.

The Solar Eclipse is a Hardmode event where the sun will rise, obscured by the moon, dramatically reducing natural light to a level darker than nighttime. Normal biome enemy spawns are replaced with special enemies that can spawn near NPCs, much more frequently and in greater numbers than usual. On the  PC version,  Console version,  Mobile version,  Old Chinese version,  tModLoader version, and  tModLoader 1.3-Legacy version, it can be skipped using an Enchanted Sundial.

During the event, the following enemies will spawn:

After all three Mechanical Bosses have been defeated:

After Plantera has been defeated:

A Solar Eclipse is always terminated upon dusk.

The Pirate Invasion is an event that is very similar to the Goblin Army. It can spawn randomly, or be summoned by the use of a Pirate Map, which can be obtained from killing any enemy in the Ocean biome during Hardmode.

During the event, seven / six different pirate themed enemies will spawn:

The event is completed after a certain number of pirates have been defeated. Afterward, the Pirate NPC will move in.

The Pumpkin Moon is a Halloween-themed event where, unlike most other events, the Pumpkin Moon takes place in distinct waves. There are 15 waves in total, which grow harder as the night wears on, culminating in the "Final Wave", which lasts for the remainder of the night. The Pumpkin Moon can be skipped using an Enchanted Sundial.

The Pumpkin Moon has seven unique enemies, in increasing order of difficulty:

Although there are no rewards for surviving the event, besides an Achievement, the enemies can drop unique items, including Spooky Wood and equipment like the Spooky Hook and Raven Staff.

The Frost Moon is a Christmas-themed event, using the same wave system as the Pumpkin Moon. The Frost Moon also has an additional five "bonus waves" after the "Final Wave", increasing the wave maximum to 20. Enemies have similar behavior to Pumpkin Moon counterparts, but are tougher, making this event the hardest on the  Old-gen console version,  Windows Phone version, and Nintendo 3DS version. The Frost Moon can be skipped using an Enchanted Sundial.

The Frost Moon has 11 unique enemies:

Although there are no rewards for surviving the event, besides an Achievement, the enemies can drop unique items.

The Martian Madness event is a post-Golem event with an alien invasion theme. It is unique from the others in that in order to start it, it is required to encounter a Martian Probe randomly in the outer parts of the surface and space levels of the world and move into its light. Once the probe detects the player, it needs to leave the screen without being destroyed.

When triggered UFOs start flying in the background.

The Martian Madness event features 11 unique enemies:

The event is completed after a certain number of Martians have been defeated.

The Lunar Events is a unique type of event that spawns four different pillars, the Celestial Pillars, spread evenly across the world. While in the proximity of a pillar, respectively-themed enemies spawn. There are four different pillars: the Solar Pillar, the Vortex Pillar, the Nebula Pillar, and the Stardust Pillar. Initially, all pillars are surrounded by a protective barrier. In order to damage and eventually defeat a pillar, a certain number of enemies related to said pillar needs to be defeated.

There are numerous unique enemies in this event:

After defeating all four pillars, the Moon Lord will spawn. The event is completed once the Moon Lord is defeated or the player dies during the battle.