"how did you come up with your syndra build"?
unfortunately(?) i have 3 PhD's worth of time spent playing league of legends in challenger, so intuition played a part.
but the truth is, it was a lot of experiments and the scientific method.
everytime a new patch hits, i test out every change. when mandate change came, I theorycrafted who this item might be viable on - liss, galio, tf, taliyah, syndra, ori, etc.
while some users were obvious (galio/liss), some champs would have to push the boundaries of their build to make it viable.
on ori, taliyah, it wasn't viable i kept going oom because you need a lost chapter item.
and when i figured out that mandate wouldn't work on these champs, i was delighted to have my hypotheses proven wrong, because that's progress.
but on syndra, i noticed that mandate replacing lost chapter worked exceptionally well - 0 mana issues, and a ton of haste.
but i didn't land on my magic pen build there. first, I experimented with substituting the meta builds - mandate + rocketbelt, super cheap for 2400 + 2650 gold, with more haste than you can ever need. even tried cryptbloom + ionians, for a total of ~120 haste.
from there, i switched out individual components - ionians for sorcs, cryptbloom for void, but these versions didn't feel much better than the meta builds, similar or lower strength at best. they felt viable, but not OP.
and that's when i remembered my full magic pen syndra build i used to go, stormsurge -> shadowflame. i ultimately had given up on that build, because it lacked haste... it did a ton of damage, but your rotations were so slow and had clear weaknesses.
but mandate provided 30 haste on E (it's 35 after buff now), which was Syndra's most important spell, and as long as you have access to E, your utility is not diminished.
so i tested it out. tried mandate into stormsurge. boom. there it was. the damage was ABSURD. the haste was there. i could instantly tell that the build i had been going prior (blackfire + cosmic) could never come close to the damage of this build, and i full shifted to this new build.
from there, i experimented with the build order. mandate -> sorcs -> stormsurge -> shadowflame seemed best, so i locked that in. sometimes stormsurge first was better in 1shottable matchups, and currently it is extremely op with t3 sorcs buff.
and for my 5th item, i originally started out going deathcap. but the item was expensive and i was overkilling, dealing way more dmg than my squishy opponents' hp bars.
i tried cryptbloom instead. BAM. a whole ton of extra haste, i still overkilled my squishy opponents, but now i dealt even more damage to tanks while getting more rotations off.
so, in conclusion, my 12 years of experience playing at a challenger level played a part, but a lot of it had to do with the scientific method. making hypotheses. isolating and controlling variables. being proven wrong. discovering what's optimal. adapting the build and creating new hypotheses. testing over and over again, with my main account's LP on the line.
and i gotta say, i'm happy with the results. I'm the highest rank I've been in years (rank 19), and syndra is my highest wr champ at 65% over 140 games. and i had a lot of fun discovering the build.
Bot-lane Sion
When my support blindpicks Janna Sona Seraphine etc
Instead of playing adc or veigar into draven nautilus with a sona, Pick sion.
unbreakable in lane, ADCs dont have good items for killing high HP tanks, the enchanter is so happy having a tank to help them lane, scale and ward.
Sona is an OP champ but painful to lane with, this solves that.
Video below!