Quas
When to use:
-Early game in lane - at early levels with proper micro and considering Kael knows how to prevent an early gank, Quas can reduce the number of healing items needed to stay in a lane, considering its not overly aggressive, (but still should have at least one set of tango for juking purposes if anything backfires) allowing Invoker to get a chicken as he is not going to carry with the Quas build... more on that later.
-When under the effect of a DPS spell. Examples: Doom, Venomous Gale, Poison Nova, Viper Strike, etc. 1/2/3/4/5/6/7 x3 HP regeneration per second is not likely to turn the tide of battle as it affects only Kael, but it sure can make a huge difference for him when he is under the effect of a DPS spell (Reminder: Each hero has 20% magic resistance). A non-under-leveled Invoker will survive any DPS spell if he does not get nuked to oblivion and keeps his distance in the battle. (Reminder #2: Invoker is very likely to get Doomed in battle...for obvious reasons).
-When going for a Quas build it is often better to have 2 orbs of Quas and one of Wex, as this is the combination for Ghost Walk and hitting R and V hotkeys is all that is needed to activate the escape mechanism (asuming default hotkeys are used). Unlike some Exort or Wexbuilds, where 3 of the same orbs make huge difference, this one does not require triple Quas. In other words 7 hp regen per second (asuming Quas is maxed) is sacrificed for easier activation of the escape mechanism. This is highly recommended because shifting orbs cancels movement and that is a bad thing to do in the heat of battle, it can make huge difference, also chain stunning/disabling will screw the sequence up. Ghost Walk is always situational and itshould not be one of the two active spells.
Wex
-Wex is used for fleeing and chasing. 2%/4%/6%/8%/10%/12%/14% AS and 1%/2%/3%/4%/5%/6%/7% MS per instance make up for the low MS of 280 and drastically boost the attack rate of Kael. Reminder: Each time Wex is leveled, Invoker gains +2 to AGIand each point in Agility gives 1% attack speed.
-At higher levels the provided mobility (increased turn rate as а result of the speed bonus) can be useful to dodge certain spells like Lina's Light Strike Array, Leshrac's Split Earth,Admiral's Torrent, Phoenix's Sun Ray, etc.
-If Wex is the prioritized skill, in most cases all 3 orbs should be set to Wex. With a Wexbuild, orbs should be set to Quas only when the opposing team has heroes with DPS spells likeDoom, Venomancer, etc. (considering Quas is at significant level), as the bonus speed is preferred than the extra HP regen. Ghost Walk is gotten situationally again, only that this time the longer sequence should be used (QQWRV, assuming default hotkeys are used), because sacrificing 2 orbs of Wex that equal 14% MS and 28% AS is rarely a good decision just for the possibility to activate the escape mechanism easier.
-If Wex and Exort are the same or almost the same levels, Wex orbs are taken over the Exortones, as the damage bonus is not as much as significant as it would be if Exort is prioritized and the speed bonuses, especially the MS one makes the difference.
Exort
-Exort provides the ultimate lane control, making last hitting a child's play. At max level it provides damage as a high tier damage item, assuming the 3 orbs are set to Exort, and that makes it 21 x3 = 63 bonus damage.
-If Exort is prioritized, the 3 orbs should be set to that instance, as the huge bonus damage is very important in the early game. Late game when both Exort and Wex are maxed, Wex is preferred if Kael opted for raw damage items. Yeah, the +61 damage is exchanged for permanent 42% AS and 21% MS bonus.
-There will be a point of time in the mid game where Exort will be maxed and Wex - either maxed as well or almost maxed. In that scenario, in order to get the best DPS possible, Exortand Wex orbs can be mixed, depending on the items obtained so far. The damage per second will be slightly higher and most of the time it won't have any effect over the game but I mention this because we are aiming for perfection here. It takes practice to decide whether or not and when you should mix the orbs. You never know... anything can happen and sometimes the smallest of details decide matches.
-Asuming with the Exort build, The Invoker has gotten at least one level of both Quas andWex, Ghost Walk is still used as an escape mechanism, but nothing else as it will slow you down a lot and your opponents - barely due to the low levels of Quas and Wex.
Invoke
-Okay, so Invoke is not necessarily taken whenever possible. Some skill builds don't require/allow you to lay down a barrage of spells (due to lack of mana, chainbreak or low orb levels in the early game which result in either nearly useless spells or such that are not worth the mana), therefore an extra orb is sometimes more useful than leveling up the ult, as its only benefit consists in decreasing the cooldown by 5 seconds. That applies after the first two levels of Invoke because the second one gives you another available spell. People tend to forget that after using both active spells in a battle, another one can be invoked right away (assuming Invoke is not on cooldown).
-For example, with an Exort oriented build the first level of Invoke can be skipped at level 2 and taken at level 4 due to the weakness of some spells in this very early stage of the game (a competent player will not die to Exort spells this early). In this scenario Exort is taken at levels 1 and 3, Quas or Wex at 2 and Invoke at 4. The second level of Exort will improve damage and therefore last hitting significantly. The first level of Wex is nearly irrevelent at level 2 as Exort orbs will be used, however leveling up Quas once will passively increase the hero's HP by 38 (2 STR = 38 HP, 19 per point) and, believe it or not, this can make a big difference in the early game. This doesn't go just for Exort orientated builds.
-Chainbreakers (Silencing, disabling and mana burning heroes) make multi-casting much, much harder. More on that later.
-Always invoke your two primary spells outside of battle in order to have Invoke off cooldown during the fight.
-Some spells are better for ganking than others. If your primary spells are not appropriate for ganking, replace them temporarily (during the gank) with appropriate ones, even if they are weaker on paper.
