Finally got to level 100.
Kekekeke.
Hoard your sanity refreshes. You want as much sanity as possible for the next event beginning 29th downtime.
Long story short, when you start playing the event, don't overdo the Obsidian.
You just need 4000 pieces.
You get 88 finishing OF1-4,6. You want to play OF7 59 times, no more, no less.
Completing your dailies will give you the remaining obsidian you need to clear the event.
This gives you 4008 obsidian. You need 4000 for clear.
With your remaining sanity, you will want to clear challenge mode and ex mode once for the first time clear.
Spend EVERYTHING else on OF-8 to gain festival passes.
The festival passes are then to be spent on OF-F4 to get you obsidian coins.
Obsidian coins are used to clear the festival lotto. The item drops are very desirable, especially the high end drops from the 6th (infinite) lotto box.
A more detailed write up here. The numbers are different because the author did not factor in the 88 obsidians dropped in the process of unlocking OF7.
https://gamepress.gg/arknights/even...rt-surging-flame-event-operations-and-farming