Senna is commonly used in both the ADC role and the support role in League of Legends, so it is important to know your way around both roles to truly master Senna; she can be both a powerful carry, and a utility powerhouse. While the roles can be pretty different from each other, one fact rings true for both; Senna requires a steady flow of Mist to fuel her power throughout the game, and these can be gathered in multiple ways. First off, Dragons, Rift Heralds, and Baron Nashor will always drop two Mists. Other monsters throughout the jungle will drop Mists, like the Brambleback and the Scuttle Crab, so keep an eye out whenever you maneuver through the jungle. Souls will drop less frequently if you are killing the minions yourself, so a support Senna has a higher chance at accumulating a large amount of souls very quickly. Either way, you want to always try to pick up these Mists before they expire, as long as it does not put you in harm's way. Enemies will try to use the placement of your souls to engage on you, so always keep an eye out for where the support and ADC are at all times, to avoid getting shut down when you move in for a soul. These Mists help Senna scale throughout the game and each one makes her increasingly more powerful. You can also utilize her Q has a way to safely snatch up Mists from afar, as any Mist that comes in contact with Q will be collected.

The final way you can get Mist is from enemies, either auto-attacking them or using an ability on them twice in a row, or collecting a Mist from them when they are killed. You can easily harass the enemy with a combination of Qs and auto attacks, granting you additional Mist in the process.

The Impact of Q

Senna's Q is an ability that pierces through all targets, hitting everything it its path between minions, enemy champions, and even ally champions. Lining up Q to both heal an ally and damage an enemy is where a lot of utility comes in for Senna, especially a support Senna. Q can also be used on wards and turrets, but keep in mind, you cannot cast Q on only yourself, as it requires an additional target. Using Q on any of these targets will automatically heal Senna. As mentioned above, you can also use Q to collect Mist that is otherwise beyond your reach.

The Impact of W

Senna's W damages targets as well as roots them after a short time. You can use this to catch an escaping enemy, engage on an opportune fight, or even to finish off the enemy's health. After Senna uses Q or auto attacks an enemy, she can collect the available soul by landing W on them, as well. Keep in mind that this ability does not ignore minions, but it will still root everything in the immediate area if it hits its target. Additionally, ADC Senna can use W to secure a cannon minion. This ability can be used defensively and offensively, whether you are preventing the enemy from catching up to you, or you want to trap them for the perfect kill. Try to only use this ability when you know it will hit, as the cool down can be deadly if an enemy decides to engage once you used up your W.

The Impact of E

Senna's E can be used as a crafty escape or a deadly engage, granting you and your allies a hidden cloak of speed. As with W, you can use E offensively and defensively, depending on the current situation. You can move up and wrap allies in the shroud and speed them away to safety, or you can boost them up to chase down the enemy. Remember not to use E if you do not really need to, as it has a hefty cool down, and you will want to have it available in times of need.

When to use R

Senna's R can be used as a finishing snipe on an enemy, or as a helpful shield for her allies. However, you want to be careful not to use this ability to only grab an assist or to try and save someone that is definitely going to die whether you use your ultimate or not. Using an ability when it is not really needed can really backfire when it happens to be on cooldown during a critical moment.

As Senna initially turns level 6, you will want to start looking out for allies who may need your help with your ultimate. If a fight is breaking out and you need to keep track of their health to know if you need to use R, it is not a bad idea to take a step back in lane so that you are not engaged on by the enemy botlane during your decision making. Otherwise, save your R for fights that may happen in your lane, or when you start to fight over the Dragon.

When to Pick Senna

Knowing when to pick a champion during champion select is key, and Senna is no exception from this. If you are first pick, whether it is for ADC or for support, Senna usually is not a bad option. However, this can backfire if your team ends up building entirely attack damage, or if the enemy botlane has a heavy engager. While Senna has a lot of range and utility, she can still he easily shut down by champions like Nautilus or Leona, especially if she misses a W or gets stunned during the cast of her R. If your team has a small amount of attack damage, Senna can end up being a key choice, even as a support, since she still builds items that cause damage.

Itemization and the Course of the Game

As an ADC, Senna will want to build Manamune first and Black Cleaver second. As for support Senna, Umbral Glaive is very important for shutting down the enemy's vision, and is a good first item. Black Cleaver is also the usual second item for Senna support. Going forward, ADC Senna will want to focus on building attack damage and critical strike chance. For Senna support, you can either build lethality if you are doing well, or pick up a Redemption to help heal your team if they need a support more than a damage dealer as the game goes on, especially if you did not do so well in lane.

As laning phase begins, you want to utilize Senna's kit to out poke the enemy botlane, but you want to stay at a safe distance. It is a good habit to develop to move in between auto attacks so that you are not as easy to predict. Your enemy will be on the lookout to engage on you, and if you are constantly moving around, it will be harder for them to land their skill shots.

Senna is not able to peel for her ADC, as she is generally very vulnerable. Although, her mobility with E can help get her out of trouble, combined with a few heals from Q, so she's not exactly helpless. Senna does not have exceptionally strong siege capabilities, so she should not be used as a split-pusher or solo laner in general.

In teamfights, Senna should stay back and attack enemies with her long range and quick Qs. She requires the safety of her team and can easily be shut down by the enemy team if they decide to engage on her. As a support, you will want to use W to catch enemies out or use it to keep them away from your allies. While utilizing E, you can quickly move your allies into position for the fight, or to help them disengage entirely. As an ADC, you will want to focus on taking down the enemy's damage dealers and healers, those who are crucial to the teamfight, but are more vulnerable than bruisers or tanks. You will want to wait for the team to engage for you, whether they create their own set up, or they act on one of your landed W's. If you are up close and personal to the action during the fight, you can easily be shut down, since your team relies on you to do the bulk of the damage as a carry. If you are in a bad position, you can use E to escape to the safety of your teammates, but you might not be able to do this every time you get caught out.

Using Senna's ultimate ability can help absorb incoming damage and give your team a boost to win the fight. This ability also does damage in the center most bar, which can help cut down the enemy's health or snipe an escaping target. Whether you are the ADC or the support, your Q can still be used to give a quick heal to an ally in need. It is a good idea to try and line up your Q with as many different targets as possible, whether they are enemies or allies.

To Summarize

Mastering Senna is all about knowing your role throughout the course of the game, and whether you are the ADC or the support, you can always utilize your abilities for both offense and defense. Senna has a lot of sustain, poke, and scaling potential paired with a root and a quick escape. However, she is not the tankiest of champions, and should never be in melee range of the enemy or at the front of a teamfight.