Booster Pack Heroes Permanent Foilium Upgrade Guide

Real gameplay reference by FungalBrainRot, observed build v1.0.27D; not official footage or proof of later patch behavior.

Which permanent Foilium upgrade should you buy first?

Spend Foilium on the upgrade that addresses your current bottleneck. This Booster Pack Heroes best permanent folium upgrades guide recommends shop flexibility for constrained shops, relic capacity when a useful relic is waiting, and Mastery Interest when you actually save Mastery. Choosing between Booster Pack Heroes best permanent folium upgrades matters because these purchases survive the observed Act 3 transition while the ordinary skill tree resets. The recorded transition shows what carries over.

First, a spelling clarification: the game’s interface calls the currency Foilium. “Folium” is the search variant used in this guide’s title. Both refer here to the currency associated with the observed permanent upgrade tree.

This guide covers Booster Pack Heroes on its official Steam page. Its mechanical evidence comes from player experience footage uploaded on November 11, 2026, with the menu displaying v1.0.27D. These observations do not establish behavior in v1.0.30D.

Use this conditional shortlist:

Your current problem	Upgrade to consider	Reason for the recommendation
Shop choices feel too limited	Cheaper Shop Reroll or Shop Slot	Another reroll or another offer can expand your options
A useful relic is waiting, but equipped capacity is full	Relic Slot	Extra capacity directly addresses that constraint
You regularly carry Mastery into Improvements	Mastery Interest	Its benefit depends on the amount stored at that point

These priorities are editorial reasoning from the observed tooltips. The footage does not establish a measured return on investment or a universal purchase sequence.

The practical rule for Booster Pack Heroes best permanent folium upgrades is to identify the limitation before choosing the upgrade. If you are still learning the overall progression, the Booster Pack Heroes beginner guide provides a companion starting point.

How do the permanent shop upgrades compare?

Shop upgrades address different problems: finding an offer, affording an offer, or changing how heroes appear. Treating them as interchangeable makes purchase decisions harder.

The Foilium tree shown in player experience footage provides the following distinctions:

Upgrade	Observed effect	Situation where it deserves consideration
Cheaper Shop Reroll	Adds one free shop reroll	You want another opportunity to inspect offers
Shop Slot	Adds one shop slot	You want more offers available together
Shop Discounts	Allows offers to receive discounts	Affordability is limiting otherwise useful purchases
Reroll Discounts	Rerolling builds a discount chance that resets when the shop phase ends	You already make repeated rerolls during a shop phase
Double Deal	Can present heroes in pairs	Paired hero offers would be useful to your plans
Triple Deal	Can present a trio of heroes	Trio offers would be useful to your plans

Start by separating access from affordability

If shops rarely show something you want, consider Cheaper Shop Reroll or Shop Slot. That recommendation follows their effects: one supplies another reroll, while the other supplies another slot. Neither tooltip establishes that you will receive a particular hero.

If useful offers appear but you struggle to afford them, Shop Discounts addresses the more relevant problem. A larger selection may be less urgent when the existing selection already contains purchases you cannot comfortably make.

Before spending, ask:

• Am I missing useful offers, or passing on useful offers because of their price?
• Would one additional reroll help me explore the shop?
• Would another visible slot help me compare options?
• Do I already reroll enough for Reroll Discounts to fit my behavior?

Keep reroll discounts within their stated window

Reroll Discounts has an important boundary: its accumulated discount chance resets at the end of the shop phase. Do not evaluate it as a discount chance that keeps building across later shops. The observed shop tooltip establishes that reset.

Likewise, paired or trio offers should be evaluated for their usefulness to you. The supplied evidence does not establish bundle prices or prove that these offers always deliver better value.

For Booster Pack Heroes best permanent folium upgrades, shop flexibility is a sensible recommendation when restricted choices are the problem. Comparing the effects is more useful than assuming every shop node belongs in a fixed ranking.

When should Relic Slot take priority?

Relic Slot has a direct effect: it lets you equip one additional relic. That capacity increase is visible in the recorded Foilium upgrade tree.

The strongest reason to prioritize it is equally direct: you have a useful relic available and your equipped capacity is already full. In that situation, you can identify what the purchase would let you do before committing your currency.

Use this decision sequence:

1. Check whether equipped relic capacity is actually limiting you.
2. Identify the additional relic you would want to equip.
3. Compare that specific benefit with the shop or Mastery problem you could address instead.

This is a recommendation based on capacity, not a measured claim about combat strength. The supplied evidence does not establish which relic combination is strongest or how much an additional equipped relic improves a particular build.

If you cannot name a relic you want to add, the purchase is harder to justify immediately. You can return to it when capacity becomes a concrete obstacle.

In a Booster Pack Heroes best permanent folium upgrades comparison, Relic Slot deserves priority when its extra space has an identifiable use. Its appeal comes from solving a known problem, rather than from an assumed universal power increase.

When is Mastery Interest worth buying?

Mastery Interest rewards stored Mastery at a specific moment. In the observed build, it grants an amount equal to 25% of stored Mastery when an Improvements phase begins, and the displayed purchase price is 10 Foilium. The recorded Mastery Interest tooltip shows both details.

The important word is stored. This is not an automatic increase applied to every point of Mastery you have earned over your entire progression.

The relevant question is therefore: how much Mastery do you expect to have saved when the phase begins?

Understand the arithmetic before setting a priority

The following values are hypothetical arithmetic examples, calculated from the observed 25% rate. They are not recorded player balances or measured payouts.

Hypothetical stored Mastery	Calculation	Calculated additional Mastery
0	0 × 25%	0
40	40 × 25%	10
100	100 × 25%	25

These examples use whole-number results and make no assumption about how fractional amounts are handled.

They illustrate why spending habits matter. A player carrying a substantial balance into Improvements has a larger base for the calculation. A player arriving with nothing stored has no balance on which to earn interest.

Match the purchase to your actual saving habits

Consider Mastery Interest when you regularly bank Mastery or have a clear reason to save it. Give other upgrades closer attention when you normally spend nearly everything before the relevant phase begins.

That does not establish that saving is always better than spending. An immediate Mastery purchase may be useful, and the supplied evidence does not measure the tradeoff between that purchase and a later interest benefit.

A practical recommendation is to review your normal balance before buying the node. Ask whether saving already fits your progression, rather than assuming the interest upgrade will automatically make every saving decision worthwhile. The Booster Pack Heroes Mastery guide is the related reading for Mastery spending decisions.

For Booster Pack Heroes best permanent folium upgrades, Mastery Interest is a conditional priority. Its displayed rate is clear; its value to you depends on the balance present at the stated trigger.

What survives the Gate to the Stars transition?

Permanent progression becomes especially relevant at the observed Gate to the Stars prompt.

In player experience footage at Chapter 7, Act 2, The Last Crucible, the gate offers the option to begin Act 3. The interface distinguishes the ordinary skill tree from the progression that carries forward. The recorded gate prompt shows these preservation rules.

Progression element	Result at the observed Act 3 transition
Ordinary skill tree	Resets
Foilium upgrades	Preserved
Foilium balance	Preserved
Collection	Preserved
Bestiary	Preserved

This gives Foilium purchases a different planning role from ordinary skill-tree spending. The observed transition retains those upgrades even while resetting the ordinary tree.

It also preserves your Foilium balance. Consequently, the gate prompt does not create an observed requirement to spend every remaining point before proceeding. Holding currency for a purchase with a clearer purpose remains an option at this transition.

Before choosing an upgrade, review the same three questions: are shop choices constrained, is useful relic capacity missing, or are you carrying Mastery into Improvements? The transition does not make those tradeoffs disappear.

A useful Booster Pack Heroes best permanent folium upgrades plan connects persistence with present usefulness. An upgrade surviving the gate is valuable context, but it does not prove which purchase should come first.

For the separate question of obtaining the currency, see the Booster Pack Heroes Foilium acquisition guide.

FAQ

What are the Booster Pack Heroes best permanent folium upgrades?

The strongest conditional recommendations are Cheaper Shop Reroll or Shop Slot for constrained shop choices, Relic Slot when useful equipment is waiting, and Mastery Interest when you bank Mastery. This is an editorial framework based on observed effects, not a tested universal ranking.

Is Foilium the same currency as folium?

In this guide, yes. The observed interface spells the currency Foilium; “folium” is the search variant. The recorded Gate to the Stars interface uses the in-game spelling when describing preserved progression.

Does Mastery Interest increase all Mastery earnings by 25%?

No. The observed effect uses stored Mastery when an Improvements phase starts. It does not apply a blanket bonus to lifetime earnings. The node displays a price of 10 Foilium in the v1.0.27D player experience footage.

Do permanent Foilium upgrades survive entering Act 3?

They are preserved at the observed Chapter 7, Act 2 gate, alongside Foilium balance, Collection, and Bestiary. The ordinary skill tree resets there. This answer concerns that recorded transition; the supplied footage does not establish rules for every later reset or another build.

Related guides

• Beginner Guide & Early Upgrades
• Best Upgrades for Early Progress
• Endless Mode & Replay Options