Read Senna's fucking essay of a passive
So she has a stack mechanic. Dope, plenty of champions have a stack mechanic. In the support role, swain or his ally has to hit hard cc and swain needs to hit his W or kill someone. Veigar needs to hit his spells or kill/assist in killing someone. Thresh has a random chance, but let's be real, thresh's base stats are so hilariously cucked that his soul system serves no purpose than to somewhat help his base stats get back to baseline with every other champ if the game even goes that long.
What does senna have to do.
She has a guaranteed soul drop chance on monsters and caddies. Ok I guess, thresh, despite all his gating mechanics like shit-tier base armor, has that too. She has a 20% chance for a mist to drop on a regular minion. Why? her base stats are...
HEALTH 520 – 1965 ATTACK DAMAGE 50 HEALTH REGEN. 3.5 – 12.85 ATTACK SPEED [*] 0.2 (+ 0 – 68%) (+ 0.425) ARMOR 28 – 87.5 CRIT. DAMAGE 130% MAGIC RESIST. 30 – 38.5 RANGE 600 MANA 350 – 1115 RANGE TYPE RANGED (NON-PROJECTILE) MANA REGEN.
Not even that bad. The fact that she doesn't gain any attack damage by level doesn't mean anything since all of her scaling is in bonus ad and she could absolutely make up for that deficiency through items alone. But her souls don't just interact with her base AD, nah that's too simplistic. So her souls do this:
Each stack of mist grants Senna Attack damage icon 1 bonus attack damage. For every 20 stacks, Senna also gains Range icon 25 bonus range and Critical strike chance icon 15% critical strike chance. Upon exceeding 100% critical strike chance, Senna converts 35% of the excess into Life steal icon life steal. Additionally, Spellthief's Edge item Spellthief's Edge item-line grants Adaptive Force icon adaptive force instead of Ability power icon ability power.
shave off the lifesteal, she doesn't need the range stack mechanic either as a base 600 range champion, especially considering the fact that the range of her fucking spells are long enough to allow her to not even have to really interact with most lane opponents. Ludicrous design.