Hey there. Just wanted to dump some thoughts I typed out regarding the major RNG points in the run. Writing them down has helped me keep in mind the areas where I can gain/lose the most time due to RNG.
Major RNG pivots (+/- 30 seconds or more)
- Bow drop time
- Necron AoE usage frequency/crits
- Hallow Mage stun length/crits (& casting paralysis on you more than twice)
Here are the slightly less relevant RNG pivots:
- Crits on Hanging Dead in poison corridor (Earth World?)
- Molebug blocking Earth World mineshaft (about 33% chance of horrible spawn that costs 5+s)
- Howler spawn pattern/crits in Monster World (sometimes get one extra/less Howler - not getting them saves time but you miss extra cunes, so less MP or HP potions)
- Pitcher enemies' Dorado's Ashes drop rate in Earth World (saves time on Edward if you would otherwise run out of arrows and Dorado's Ashes)
- Extra (up to 2) Molebugs blocking Earth World bridge before Apollos (~10s per extra bug over the 2 that always spawn)
- Apollos casting paralyze (you can lose up to 20 seconds here under full paralysis (if you don't die), but rarely)
- Fire World corridor Watchtower spawn before lava river (can sometimes run straight past even if you get it)
- Ebony Knight AoE frequency (usually doesn't matter but he can troll)
- Paralysis by flying fish when warping to fight Magi Magus
- Magi Magus bracelet drop (uncommon drop, more damage against Balron/Edward)
- Jester bracelet drop (uncommon drop, more damage against Balron/Edward)
- Hallow Mage Endless Amulet drop (common drop, more damage against Balron/Edward)
There is also the Wizard Crown that can drop from the 4th (uncommon) Molebug spawn before Apollos. This causes your spells to do significantly more damage (most useful against Apollos/Ebony Knight/Balron), but you trade ~10s by having that 4th spawn appear at all.
Note: RNG related to enemy AI is not fully understood. Many enemy actions are at least in part dictated by player positioning, but this does not seem to apply to Necron/Ebony Knight in a way that is usefully manipulable yet.