Just finish all the reward stages, so I’ll try my best to answer my own question.
Worth to do it? Yes.
so many Shards and Treasures, with extra Vault Key, Diamonds, and 2 Minor Chaos Orb.
Minimum Tier? Just 2 (90 gems)
Except you need a new weapon, then go for it.
Best Strategy? Clear all stage until level 100, then stop.
Use your best team for it. In actual Underworld, it’s easy enough to farming for end-gamers and doing fraction challenge.
On one of Tacet’s streams, he was able to get “very” lucky and get a quality upgrade with far less than 90%. You just had bad luck. This is why I don’t bother with the RNG and only do it at 100% until I max quality.
My upgrade strategy is haphazard and probably not optimal but whatever.
If I have 5 of the cruddy 5% treasures, I use them up on the spot. They don’t provide enough of a boost for me to care, and 25% is better than 0%.
Otherwise, I don’t try to upgrade unless I have at least one 25% or higher treasure. I use exactly one, then see if I can bump it up to 85% or greater with the cheap treasures. If not, I wait.
I can afford to use “too many” cheap treasures, but I’d rather get 2 80% chances out of 2 of the rare ones than 1 100% chance. I can still fail, but it’s more likely I’ll get 2 upgrades.
Question: During a normal delve (so NOT an event delve) if I want to keep it at it’s current lv would it be better rewards to play on x1 and beat the boss, or play on x2 and retreat before the boss?