• Affects all sources of damages apart from most auto attack related sources of damage and the damage deal by any summons/illusions.

• Here is a list of abilities and damaging effects that Spell Damage does NOT affect:

Spell damage affects all other sources of damage. For example: it does the damage done by Kil’jaeden Finger of Death ability, the damage done by Tinker with the Naga Sea Witch synergy, the damage done by the Firelord’s Metors and even the damage done by immolation items.

• Cooldown reset is an effect that grants most tower a chance to immediately use their active ability again, therefore bypassing their usual cooldown.

• For the sake of balance, cooldown reset does NOT work for the towers listed below:

• Both respectively function as critical chance and critical damage. Each tower has an innate 5% excellent rate to deal 25% more (excellent) damage.

• Excellent Rate and Excellent Damage do NOT apply to any damage dealt by summons/illusions. It applies to all other sources of damage, even the damage dealt by immolation items.

• Note that reaching more than 100% Excellent Rate provides no benefit.

• Increases the duration of summons. The less intuitive thing about it is that not all summons benefit from it: Illusions created by Illidian, illusions created by the Huntress from the Priestess of the Moon synergy, beetles spawned by the Crypt Lord, and any summon spawned from Scourge Bone Chimes, Voodoo Doll or Razor Spine items all have fixed duration that cannot be increased.

• A stat that grants towers a chance to summon more powerful versions of their summons (a 150% damage increase). Towers that don’t benefit from Perfect Summon are the same as the one that don’t benefit from Summon Duration.

• Getting more than 100% perfect summon chance provides no additional benefit.

• Reduces the duration of stun and silence effect that some creeps or bosses can have. It is a deceptively important stat for some of the Raid mechanics, or to compete for fast boss timer kills.

• Getting more than 100% Stun and Silence resistance provides no additional benefit.

• Armor reduction is one of the most important stat in the game, especially when playing on higher difficulties. It is particularly significant to farm kill gold on Gold rounds and to greatly improve damage against bosses.

• There are four items that provide armor reduction: Orb of Darkness, Orb of Corruption, Wand of Shadow Sight, Thunder Phoenix Egg.

• In an end game set up, players usually put Orb of Darkness, Wand of Shadowsight and Thunder Phoenix Egg in one tower and Orb of Corruption in a different tower. 

• As detailed in the Orb of Corruption and Orb of Darkness descriptions, these two items should not be put in certain towers.

• A stat that increases the hp of summons. Summons from tier 1/2/3 towers respectively have 1/2/3 hp.

• There are several monsters in the game that can damage summon health. For a summon to be unaffected by the dispel cast by a boss or Raid boss, the summons’s hp must be equal or greater to the damage dealt by the dispel.

• It is important to note that Dragon’s dispel deal 2 damage to summons, that the wave 30 boss deals 4 damage to summons, and that Final boss deals 4 damage to summons every 10s and will also deal 5 damage to summons once its hp reaches 10%. For builds that rely on damage from summons, this is a very important stat to prioritize to win a game.

• Note that not all summons are affected by summon hp increases: Crypt Lord’s beetles, Huntress illusions, and creatures spawned by Scourge Bones Chimes, Voodoo Doll, Razorspine are all unaffected by increases to summon hp.

• On top of increasing the hp from the tower’s summons holding either Staff of Reanimation or Scroll of Legions, these two items provide an aura that increases the attack speed of all summons/illusions, without any exception.

• Immolation damage is a very good source of damage that can help newer players to clear waves. A tower will only apply their highest immolation damaging effect on nearby enemies. 

• It is worth noting that two towers can both apply the same immolation effect to an enemy.

• For example, if the player has two towers equipped with a Shield of Honor, enemies will be affected by both immolation effects. It is also worth noting that Immolation damage is affected by Spell Damage, Excellent Rate and Excellent Damage.

• The damaging effect of items like Firehand Gauntlets or Grimoire of Souls cannot be stacked by equipping the tower with multiple copies of the same item.

• However, different such effects do stack together, meaning that a tower holding both Firehand Gauntlets and Grimoire of Souls will have a chance to apply one (and only one) of these effects on each autoattack.

• It is also worth nothing that these effects are affected by Excellent Rate, Excellent Damage.

• Contrary to popular belief, towers max attack speed is not capped at a bonus 400% (including bonus from Agility).

• Melee towers (towers that do not fire a projectile on attack) like Mountain King, Death Knight or Maiev have a basic cooldown time (BCD) of 1.6, while non-melee towers like Illidan, Priestess of the Moon, Kael have a BTD of 1.8.

• Agility provide increased attack speed (IAS) according the following formula : 

IAS = (0.01 * Tower’s agility) + %Attack Speed from other sources. (items,skills,runes, etc.)

• Both BTC and IAS define a tower’s attack speed as follow:

Attack Speed = BCD / (1 + IAS)

For example, Maiev with 400 agility and 30% attack speed from Ghoul Frenzy rune lvl 3 would have an Attack Speed of: 1.6 / 1 + ( (0.01 * 400) + 0.30) = 0.302, where as a Maiev with only 400 agility would have an attack speed for 1.6 / 1 + (0.01 * 400) = 0.320.

• The lower the attack speed, the better. 0.01 is best.

• Here is a table that show (this excludes any effect increasing attack speed from ability):

• Stacking multiple copies of the same item will only grant that item’s passive bonus one time.

• For example, equipping a tower with two Staff of Sanctuary will only result in an increase of 30% Spell Damage, and an increase of 56 to all of its primary stats (Str/Agi/Int).

• However, stacking the increase to a passive tower bonus form two different items does work.

• For example, equipping a tower with a Staff of Sanctuary and an Essence of Aszune will result in an increase of 50% Spell Damage, and an increase of +40 to all of its primary stats (Str/Agi/Int).

• The only exception to this rule are CDR and Immolation damage.