Vanilla Mechanics
Autoswing / AutoReuse - The ability for a weapon to keep firing/swinging if you hold the attack button down. Weapons which do not have Autoswing/AutoReuse will require the button to be pressed again to be used again.
Buff/Debuff Caps - The maximum number of buffs/debuffs allowed to be inflicted on any given enemy or the player. The player maximum is 44 and the enemy maximum is 20.
Critical Chance (crit or crit chance for short) - Almost all damage sources from the player can inflict Critical damage. A Critical hit will always deal double damage (though it is still subject to defense). No matter what your stats and equipment, the DEFAULT critical chance is always 4%. Certain weapons add a bonus critical chance, and various equipment and buffs can increase it as well. A Critical hit chance that is higher than 100% confers no additional advantage; the player will deal a critical on every hit. Notably, Summon damage does not typically inflict critical hits except under certain special conditions.
Damage (dmg for short) - Literally the damage dealt by an enemy or weapon. The damage listed is reduced by the target’s defense stat, and then it will be applied to the enemy or player. There is an inherent randomization effect on all damage dealt, which causes damage to fluctuate slightly both above and below the listed value. However, the average amount of damage done per hit will match the listed damage value.
Damage Reduction (DR for short) - Decreases damage taken by a percentage. For example, the Worm Scarf grants 17% damage reduction, which simply reduces all damage taken by 17%.
Defense (def for short) - Reduces damage taken by a flat number. In Classic Mode, and for enemies in every difficulty mode, every 2 points of Defense reduce damage by 1. In Expert, every 1.5 points of Defense reduce player damage by 1. In Master, every point of Defense reduces player damage by 1.
Defense Penetration - Some player attacks have the ability to “ignore” a certain amount of enemy Defense. This will not directly increase the maximum amount of damage they can do, but it will reduce the effect of enemy’s defense. A weapon that penetrates 20 Defense will do full damage with no reduction to any enemy that has up to 20 Defense, after which point, Defense will reduce it normally. Some attacks have a low damage, but a high defense penetration, which ensures that they deal a more consistent amount of damage on enemies of different levels of defense.
Difficulty Mode (Enemy Stats) - Generally referring to Classic, Expert, and Master mode. Many enemies have different stats depending on the difficulty mode in question, such as increased health or damage. For example, a Blue Slime has 25/50/75 health, depending on difficulty. Base Journey difficulty stats are roughly half of Classic.
Frames (Time) - There are 60 “frames” in every second. If a weapon has a Use Time of 30, then you can use it twice per second (30 + 30 = 60). This impacts some other aspects of gameplay as well, such as Immune Frame times.
Immunity Frames (iFrames for short)
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Overview - When an enemy is hit by a piercing projectile (a weapon, projectile, or minion that can hit multiple times), the game has to use what is called immunity frames to prevent the enemy from taking damage from the projectile repeatedly every single frame, which could otherwise be as many as 60x hits a second. After hit, the enemy becomes temporarily immune to being hit again, though this duration is almost always measured in fractions of a second, which is more than enough for most projectiles to move through the enemy and be on their way. Particularly slow projectiles may still hit a target multiple times, but their immune frames prevent them from hitting every single frame, so this is within expected behavior. The amount of immune time inflicted by a projectile can be adjusted to make it hit more or less frequently. Immune frame time does not apply to non-piercing attacks (regular bullets, for instance, which only hit once).
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Global Immunity - By default, all piercing weapons in the game inflict what is called global immunity when hitting enemies. These enemies become invulnerable to ALL sources of piercing damage, including other types of attacks, for the duration of that period. This period is typically a default of 10 frames (1/6th of a second), but can be changed to allow faster or slower hitting. This was the original implementation of Terraria’s immune frame system, though it has been slowly shifted away from. An unfortunate consequence of global immunity is that it “blocks” you from doing damage with different types of damage sources. Unless manually set otherwise, all piercing projectiles in the game, especially older ones, use the global immunity system.
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Static Immunity - This form of immunity will still induce immune time, but this immune time will ONLY block damage from that specific TYPE projectile. Though repeated hits from the same type of piercing projectile during the immunity period will not be able to land, hits from any other type of piercing projectile WILL be able to deal damage. Though Static projectiles will not interfere with other sources of damage, there are still scenarios where firing multiple projectiles of the same type will be counter productive. For example, putting Jester Arrows (which inflict Static Immunity) on Tsunami will result in only one of the piercing arrows hitting, because the enemy will be temporarily immune to Jester Arrows as the other arrows pass through. Most projectiles that use static are balanced around this.
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Local Immunity - Finally, the third type of piercing projectile behavior is called Local. It will still induce immune time, but this immune time will only apply to the exact specific projectile which did the damage. This means that if you have two of the same type of Summon minion using local immunity, EACH minion will operate on its own independent immune timer, and they will not conflict with each other at all, nor will they block damage from any other sort of piercing damage. Local projectiles will never interfere with your ability to land hits with other projectiles, nor will firing large quantities of a local projectile be inefficient or fail to land hits.
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Non-Piercing - Technically not a 4th type, projectiles which do not pierce (which is to say, they disappear immediately upon hitting an enemy the first time) are not subject to any of the above systems. They will always deal their damage immediately, without a period of immune frames, as there is no reason for them to use such a system. They are also not impacted by the immune frame time inflicted by other types of piercing projectiles.
Knockback (kb for short) - Almost all attacks against enemies inflict knockback. The amount of knockback is increased by a multiplier on a weapon’s knockback stat, and then reduced by the enemy’s knockback resistance.
Minion and Sentry Slots - All Summon Minions and Sentries take up a “slot” to use. Players all have 1 Minion Slot and 1 Sentry Slot available at all times; various buffs and equipment can increase this quantity. With additional slots, the player can summon more active minions or sentries. Some Summon minions grow stronger/bigger when expending extra Minion Slots on them, instead of gaining additional Minions. For example, you only ever have 1 Stardust Dragon, but its size and damage increase with every additional Minion Slot spent on it.
NPC Slots - Enemies all take up a certain number of “slots”. At any one time, there is a enemy slot capacity, dictating how many enemies can spawn. Once this slot capacity is reached, most enemies will stop spawning, though it will not forcibly remove enemies over the capacity. Certain factors can increase or decrease this slot cap, such as Blood Moon, Battle Potion, or Calming Potion. Furthermore, some enemies can have a slot count that is higher or lower than 1. Enemies such as bosses or minibosses may take up extra slots since they are more of a threat than regular enemies.
Piercing and Pierce Count - The ability for a projectile to continue on after hitting an enemy, and hit additional enemies or to hit the same enemy again. The Pierce count stat indicates how many times a projectile can hit. For example, a pierce count of 5 will allow up to 5 enemies to be hit before the projectile vanishes/stops hitting. Some projectiles have no pierce limit at all.
Piercing Damage Reduction - Some weapons will deal less damage each time they Pierce an enemy. For example, a weapon with a 20% Piercing Damage Reduction modifier will do 20% less every time it pierces. In such a scenario, it might deal 100 damage on the first hit, 80 damage on the second hit, 64 damage on the third hit, and so on.
Post-Death Invincibility - Immunity frames gained directly after respawning. Duration of these frames is by default 3 seconds.
Scale - Scale is modifier which can be used to increase the size of weapon sprites, typically swords. The size of swords is normally exactly the same as their sprite, but the scale modifier can make them visually larger in game, which also allows them to reach further distances when hitting enemies. For example, increasing the scale of a weapon from 1 to 1.3x will increase its size and range by roughly 30%.
Summon Tag Critical Chance (tag crit for short) - Due to summons not being able to land critical strikes for whatever reason, the Morning Star and the Kaleidoscope apply a set crit chance for all summons upon striking an enemy. For example, if I struck an enemy with the Morning Star, which has 12% summon tag critical chance, all minions and sentries would then have a 12% crit chance when hitting that enemy. Monk Armor and Shinobi Infiltrator Armor set bonuses also grant Lightning Aura Staves a set crit chance of 16.67% and 25% respectively.
Summon Tag Damage (tag damage for short) - An effect applied by some whips that increases the damage of minions and sentries by a flat amount. For example, the Morning Star has 8 tag damage. Upon striking an enemy with it, all summons deal 8 extra damage to it.
Traveling Merchant “Rarity” Tiers - All of the items the Traveling Merchant sells are organized into 6 different “rarity tiers”, with items in the higher tiers being more rare than items in the lower tiers. Moving items between tiers will have a significant impact on how commonly he sells them.
Use Time (UT for short) - The time between swings/uses on a weapon or item. If a weapon has a Use Time of 20, this means that after using a weapon, 20 frames must pass before you can use it again. The lower the number, the faster a weapon is. A higher number is slower. You cannot directly see an item’s Use Time number in game, but it is reflected in its speed tooltip (Fast, Very Fast, etc)
UseTurn - A feature present mostly on certain autoswing swords. If a weapon HAS Use Turn, moving left and right while swinging the sword will make the sword and the player change directions. If a weapon does NOT have Use Turn, the player will continue facing the direction they were when they started swinging.
Dark Gaming Mechanics
Anti-Cheat/TrueSSC (Survival) - The bane of mobile players A system detecting unrealistic stack sizes and items which you couldn’t get with normal progression. For example, Zenith before Moon Lord, or a stack of 1029392 Dirt Blocks. Additionally, Anti-Cheat does occasionally delete fishing loot. While rather irritating, you can significantly reduce chances of this happening by simply moving away from your bobber.
Mobile users currently also experience some additional issues, such as being unable to craft crafting recipes unique to 1.4.1+, such as the True Excalibur or True Night’s Edge recipe, or Titanium/Adamantite Bars. This specific issue should be fixed sometime in the near future, though.
Damage Caps (PvP) - A limit on minimum or maximum damage dealt. For example, a weapon with a minimum damage cap of 20 damage and a maximum damage cap of 100 can deal a minimum of 20 damage per hit and a maximum of 100 damage. Note that some weapons (mainly unmodded ones) do not have damage caps.
Enemy Buffs (Survival) - Certain enemies are buffed on DG survival.
(Table taken from Survival Boss/Mob Modifications.)
| Enemy | Scale |
|---|---|
| Bone Serpent | x3 |
| Hellbat | x1.8 |
| Lava Slime | x3 |
| Fire Imp | x2 |
| Burning Sphere | x3 |
| Demon | x3 |
| Blazing Wheel | x3 |
Warps (Survival - There are warps in Survival:
- /warp jungle
- /warp surface
- /warp caverns
- /warp locean (left ocean)
- /warp rocean (right ocean)
- /warp hell (center hell)
- /warp lhell (left hell)
- /warp rhell (right hell)
- /warp spawn (spawn platform)
- /tpnpc “NPC name” (teleport to specific NPC)
Boss Scaling (Survival) - Buffs bosses that are fought before their respective timers. Anti-Rush just means a boss simply cannot be summoned before that given time.
(Table taken from Survival Boss/Mob Modifications.)
| Boss | Base Difficulty | Time After Reset Until Boss Hits Base Difficulty | Is affected by Anti-Rush? |
|---|---|---|---|
| King Slime | 1.0 | - | - |
| Eye of Cthulhu | 1.0 | - | - |
| Eater of Worlds | 1.0 | 1 day | - |
| Brain of Cthulhu | 1.0 | 1 day | - |
| Queen Bee | 1.0 | 1.25 days | - |
| Skeletron | 1.0 | 1.5 days | - |
| Wall of Flesh | 1.0 | 2 days | - |
| Twins | 1.0 | 3 days | - |
| Destroyer | 1.0 | 3 days | - |
| Skeletron Prime | 1.0 | 3 days | - |
| Empress of Light | 0.8 | 3.5 days | - |
| Plantera | 1.1 | 4.5 days | - |
| Golem | 1.2 | 5 days | Yes |
| Duke Fishron | 1.2 | 5.5 days | Yes |
| Cultist | 1.2 | 6 days | - |
| Moon Lord | 1.0 | 6 days | - |