Bottom of the tree before the top

The forge keeps climbing in the background, but the real mid-game lever is the tech tree. And its buy order is not a matter of taste: it is arithmetic.

The rule that decides everything

A node's cost does not depend on its effect, only on its tier. A tier-0 node costs 328 potions for its 5 levels; the same node at tier 4 costs 26,326 — 80 times more, for an effect of the same order.

Tier	Cost (5 levels)	Research time	× tier 0
0	328	0.1 d	×1.0
1	1,766	2.6 d	×5.4
2	5,968	6.6 d	×18.2
3	12,534	10.6 d	×38.2
4	26,326	17.0 d	×80.3

How to read

The 47 tier-0 nodes across the three trees cost, all together, 15,416 potions — that is less than a single tier-4 node (26,326). So the rule is absolute: finish tier 0 across all three trees, then tier 1, and so on. Never buy a high-tier node while a low-tier one is unbought, however much you like its effect.

The three trees

Tree	Nodes	Full cost	Research
Forge	50	469,220	369.3 d
Power	100	938,440	738.5 d
Skills, Pets & Tech	85	797,674	627.7 d

Potions come from Zombie Rush — it is the only dungeon that pays them. With 2 keys a day, every key spent elsewhere is a day of research lost. From mid-game on, Zombie Rush becomes your default dungeon.

Sub-stats change the game

Until now an item was just a damage/health pair. From age 3 it also rolls 1 sub-stat out of 13 possible ones (crit, life-steal, attack speed…), each within its range. Re-forging for a good roll starts to make sense — not before.

Age	Sub-stats rolled
0	0
1	0
2	0
3	1
4	1
5	1
6	1
7	2
8	2
9	2

Skills: three slots, not four

You only equip 3 skills out of 18. A skill is not worth its raw value but its value × its uptime: most run 56 % of the time (10 s active / 8 s cooldown). Summon tickets come from Ghost Town: that is where your skills' rarity is decided, and rarity is what sets their order of magnitude.

Forge at max tiers (level 20) and tier 0 done → End-game guide