Often finding herself in the team's backlines, Senna is damaging support that aids her team by empowering their auto-attacks.
Due to her traits, she can be played in 2 ways primarily.
In Light comps, she is extremely dependable on having Guardian Angel to survive incoming assassins and backline threats, Morellonomicon is her core item as it helps her fellow Light units to apply the % Max HP/healing debuff to entire enemy compositions.
In Shadow comps, however, she has her ability autos amplify by her Shadow buff, with Jeweled Gauntlet and Infinity Edge together for extreme burst as her fellow Shadow units can apply her destructive critically empowered autos to deal devastating damage.
Active - Piercing Darkness: Fires a beam through her furthest ally (or a nearest enemy if there is no ally), dealing 50 / 100 / 150 magic damage to enemies hit by the beam, and granting allies 25 / 45 / 75 bonus magic damage on-hit for 5 seconds.