Rubies fund everything, and farming efficiency is a hero-selection problem. The golden rule: farm the highest stage you clear quickly - a fast clear always beats grinding a harder stage slowly.
How the ruby loop works
Keys run farming rounds; each round levels fodder heroes (four per round on most stages), and every maxed fodder converts to 20 Rubies through the Ruby Farming Expedition. So rubies-per-day is simply: keys × rounds ÷ maxed fodders × 20. Higher areas give more EXP per round, which means fewer rounds per fodder - from Area 11 onward the math improves meaningfully, and event/Nightmare stages push it further.
Free daily keys
You collect roughly 780 keys per day as a pure F2P, and about 1,100 with all three subscription packs. Free keys alone keep the loop profitable - everything below is about whether bought keys pay for themselves.
Which key packages to buy
- Package A (1,000 Rubies - 1,200 keys): PROFIT. Buy it instantly, every day. It pays for itself at any reasonable farming stage.
- Package B (+4,000 Rubies - +3,000 keys): loses rubies on its own. Combined with your free keys and Package A you still come out ahead overall - buy it from Area 11 onwards if you want the extra EXP, gold and progression rather than pure ruby profit.
- Package C and beyond: a net ruby loss even at Nightmare stages. A+B+C runs about a thousand rubies negative at the best stages, and A+B+C+D is deeply negative everywhere. Only buy these for progression speed, never for rubies. (Package E is whale territory.)
Free farmer
Rei is given for free, and as a double 5-target AoE crowd-control unit she can carry your early Adventure pushing as the main DPS.
Low-investment farmers (work at T0)
Kyle, Lu Bu, Reginleif, Klahan, Velika all farm effectively without transcendence, letting newer players farm higher stages immediately. Lu Bu gets significantly better with each transcendence.
3-target farmers
The first map of each area (X-1) only spawns 3 enemies per phase, so 3-target attackers clear it perfectly - a great entry point: Ryan, Nezha, Ruri, Bidam, Yu Shin, Taka, Feng Yan, Sera, Jin.
T2 farmers
Freyja, Teo and Yeonhee step up a gear at T2 (some need it to function as farmers at all). Freyja becomes one of the best farmers in the game once she gets there.
The T6 endgame: O'Mok
Not something a new player can reach soon, but O'Mok at T6 is the strongest and fastest farmer in the game - he kills every enemy with a single skill. A long-term goal worth knowing about.