Senna vs Lulu

Attack the souls held by the Mist whenever you can: each soul freed with Absolution (passive) increases your AD, attack range and crit chance.

Fire Piercing Darkness (Q) through an ally or an enemy to hit both: the beam heals your allies, and damages and slows enemies in the line.

Cast Last Embrace (W) on a target that's already slowed or immobilized: after a short delay, they and nearby enemies are rooted.

Cast Curse of the Black Mist (E) to engage or escape with your team: allies who enter it are camouflaged, then fast and unselectable.

Cast Dawning Shadow (R) to save an ally across the map: the beam has unlimited range and shields allies.

Dodge Glitterlance (Q): two bolts fly out, one from Lulu and one from Pix, and each one damages and heavily slows.

Engage in two steps: make her use Whimsy (W), then re-engage during its 18-second cooldown.

If you can reach her, focus her in teamfights: Whimsy (W), Help, Pix! (E) and Wild Growth (R) are mostly there to protect her allies.

When Wild Growth (R) enlarges one of her allies near you, back off: anyone close to them is knocked into the air, then the aura slows them.