Sand Raiders Tech Tree Upgrades & Unlock Costs

This page explains the Sand Raiders tech tree in the popular mobile game Last Fortress: Underground, detailing each upgrade’s unlock cost and what it does. You enter your current tech level and the target level to see the total cost in gold and research speed-ups, or you can read the full breakdown below. The calculator gives you the exact resource and time investment needed to plan your progression efficiently.

Formula

The total gold cost is calculated using the geometric series formula for a growing cost per level:

Total Gold = Base Cost × ( (1 + Growth Rate)^Current × ( (1 + Growth Rate)^(Target – Current) – 1 ) / Growth Rate )

Where:

• Base Cost is the gold cost of level 1 (varies by tech, typically 8,000–15,000 gold).
• Growth Rate is the percentage increase per level (usually 20% for Sand Raiders).
• Current Level is your current tech level (1–10).
• Target Level is the level you want to reach (up to 10).
• Total Research Time is estimated as 60 minutes × 1.1^Current per level, a rough average.

Worked Example

Suppose you are at Sand Raiders level 1 and want to reach level 10. Base cost is 10,000 gold, growth 20%.

1. Calculate the growth factor: (1 + 0.20)^1 = 1.20
2. Calculate the number of levels: 10 – 1 = 9
3. Apply the formula: 10,000 × (1.20 × (1.20^9 – 1) / 0.20)
4. 1.20^9 = 5.15978, so (5.15978 – 1) / 0.20 = 20.7989
5. Total = 10,000 × 1.20 × 20.7989 = 249,587 gold (rounded)
6. Research time: 9 levels × 60 × 1.1^1 = 594 minutes ≈ 9.9 hours

So from level 1 to 10 costs roughly 250,000 gold and about 10 hours of research time (without speed-ups).

What Are Sand Raiders Tech Upgrades?

Sand Raiders is a tech tree branch in Last Fortress: Underground, focusing on improving your hero’s combat effectiveness, particularly for PvP and high-level PvE content. It includes upgrades that boost hero attack, defense, HP, and special abilities like raider damage. Each upgrade has a level (usually 1–10) and costs gold, and sometimes other resources like iron or food, plus research time. The tree is divided into several sub-branches, each with its own specific upgrade.

How to Unlock Sand Raiders Tech

To access the Sand Raiders tech tree, you must first reach a certain hero level and have the appropriate hero type (Raider class). Typically, the tech becomes available after you unlock the Research Center at level 10 and have a Raider hero at level 20. Once unlocked, you can spend gold and research points to upgrade each node. Each node’s cost increases with each level, following the formula above. You can also use speed-up items to reduce the research time.

Complete Upgrade Costs (Levels 1–10)

Here is a typical cost table for a single Sand Raiders upgrade (e.g., Raider Attack), assuming a base cost of 10,000 gold and 20% growth per level:

• Level 1: 10,000 gold, 60 min
• Level 2: 12,000 gold, 66 min
• Level 3: 14,400 gold, 73 min
• Level 4: 17,280 gold, 80 min
• Level 5: 20,736 gold, 88 min
• Level 6: 24,883 gold, 97 min
• Level 7: 29,860 gold, 106 min
• Level 8: 35,832 gold, 117 min
• Level 9: 43,000 gold, 129 min
• Level 10: 51,600 gold, 142 min

Total for one upgrade from level 1 to 10: approximately 259,591 gold and about 14.3 hours. Note that actual costs may vary slightly depending on the specific upgrade and any discounts from alliance tech or events.

How to Choose Which Upgrades to Prioritize

Not all Sand Raiders upgrades are equally valuable. Focus on those that boost your main hero’s damage output, such as Raider Attack and Raider Crit, before defensive stats. If you are a free-to-play player, prioritize upgrades that cost less gold and give the most immediate benefit. Typically, the first few levels are cheap, so it’s wise to get every upgrade to at least level 3 for a solid baseline. For PvP, max out the Raider Damage upgrade first, as it directly increases your hero’s burst potential.

Common Mistakes and How to Avoid Them

One common mistake is ignoring the gold cost growth—players often underestimate the late-level costs. Another is not using speed-ups efficiently; save them for the higher levels (7–10) where research times are longest. Also, don’t neglect the prerequisite techs; some Sand Raiders upgrades require other techs to be at a certain level. Always check the exact requirements before starting a long research. Finally, remember that research time can be reduced by alliance perks, so join an active alliance to get those bonuses.

Comparing Sand Raiders to Other Tech Trees

Sand Raiders is one of several tech trees in the game, alongside Vehicle, Infantry, and Support. Compared to Vehicle tech, which boosts vehicle durability, Sand Raiders focuses purely on offensive power. Infantry tech provides HP and defense, making it better for tanking. Support tech offers utility like healing and resource production. For a balanced army, you’ll need to invest in multiple trees, but Sand Raiders is essential for any Raider hero-centric strategy, especially for raids and quick strikes.

Frequently Asked Questions

How much gold does it take to max out a Sand Raiders upgrade?

Maxing a single upgrade from level 1 to 10 costs roughly 250,000–300,000 gold, depending on the base cost and any discounts. The exact amount can be calculated using the formula above with your specific base cost.

Can I reset my Sand Raiders tech points?

Yes, you can reset tech points using a Tech Reset item, which you can obtain from events or the alliance store. However, it usually costs real money or a significant amount of in-game currency, so use it sparingly.

What is the fastest way to get gold for tech upgrades?

Participate in alliance events, complete daily quests, and raid other players’ bases. Also, upgrading your gold production buildings and using gold boosters can help. Avoid spending gold on unnecessary items.

Do Sand Raiders upgrades affect all heroes or just Raider class?

Most upgrades in the Sand Raiders tree specifically affect Raider class heroes. Some may have a global effect, but the majority are class-specific. Always read the description to know which heroes benefit.

Is it worth maxing out Sand Raiders tech before other trees?

It depends on your playstyle. If you rely heavily on Raider heroes for attacking, then yes, maxing Sand Raiders is worth it. However, a balanced approach is often better for defending and overall progression. Consider your hero lineup and goals.

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sel tech | Tech Type | Combat=1, Development=2, Production=3 | 1
in current | Current Level | - | 1 | 0
in target | Target Level | - | 10 | 0
in cost_base | Base Gold Cost | gold | 10000 | 0
in cost_growth | Gold Cost Growth % | % | 20 | 0
out total_gold | Total Gold Cost | gold | cost_base * (pow(1 + cost_growth/100, current) * (pow(1 + cost_growth/100, target - current) - 1) / (cost_growth/100)) | 0
out total_time | Total Research Time | min | (target - current) * 60 * pow(1.1, current) | 0