SD Gundam G Generation ETERNAL: Gundam F90 Challenge Floor 20 Guide

To clear Floor 20 of the Gundam F90 (Mars Independent Zeon Forces Type) Challenge stage in SD Gundam G Generation ETERNAL, bait the boss on Turn 1 with a dedicated defensive tank while positioning your damage dealers outside its attack range. Once the boss closes the distance, soften it with stat debuffs, outrange its retaliatory strikes, and execute a synchronized link burst to defeat it before its high-damage special attacks can wipe your squad.

Recommended Squad Composition

A successful run relies on balancing single-target burst damage with defensive mitigation. Relying entirely on offensive units without defensive tools usually leads to fast attrition against the boss's counterattacks.

Role	Primary Function	Key Traits and Mechanics
Dedicated Tank	Lure initial aggro and absorb EX attacks	High DEF, Guard skills, damage reduction passives
Primary DPS	Burst down the boss through heavy armor	High critical rate, single-target EX skills, range 3+ physical or beam weapons
Debuffer	Reduce boss defense, evasion, and attack	Armor-reduction skills, accuracy downs, attack debuffs
Secondary DPS	Clear escort units and join link attacks	Balanced attack stats, flexible attack ranges
Support / Buffer	Boost damage output and sustain the vanguard	Squad-wide attack buffs, Tension generation, single-target repair

Turn 1: Threat Spacing and Escort Management

Do not rush your fragile units forward on the opening turn. The Mars Zeon F90 possesses high mobility and lethal counter options, requiring controlled board positioning.

Advance the Tank: Move your primary tank to the outer edge of the enemy threat zone to draw the boss's opening attack.
Hold Back Squishier Units: Keep your debuffer, support, and damage dealers at least one tile outside the boss's combined movement and weapon range.
Eliminate Escorts: Use your secondary DPS to clear any minor escort units that spawn near your units. Removing escorts protects your tank from chip damage and stops enemy support assists from triggering.
Position Central Auras: Move your support unit into a central position so turn-start passive buffs reach both your vanguard tank and trailing damage dealers.

Turn 2: Mitigating the Boss Threat

Once the Mars Zeon F90 advances into engagement range, prioritize controlling its output before committing heavy attacks.

Apply Debuffs First: Lead with your debuffer to lower the boss's attack and defense values. Lowering its attack cuts lethal critical-strike potential, while stripping defense makes your follow-up strikes significantly more effective.
Exploit Weapon Ranges: Inspect the Mars Zeon F90's counterattack ranges before committing an attack. Attack from range 3 or beyond using beam rifles or physical artillery to deal damage without taking retaliatory fire from its high-damage close-range weapons.
Adopt Diagonal Formations: Avoid lining units up directly adjacent to or in straight rows with the boss to minimize exposure to piercing or linear attacks.
Rotate Support Defense: If your tank's health drops low, ensure adjacent units with defensive passives are ready to intercept incoming hits using support defense.

Executing the Burst Phase

Once the boss is debuffed and within kill range, coordinate your squad to finish the encounter in a single turn.

Activate Buffs: Use your support unit's skills to grant Tension or squad-wide offensive increases.
Reapply Defense Reduction: Confirm the boss's armor debuff is active so incoming burst damage reaches maximum output.
Set Up Link Attacks: Move your remaining squad members adjacent to your primary damage dealer to trigger assist mechanics and link attack bonuses.
Fire Primary EX Skills: Launch your main DPS unit's highest-yield single-target EX skill against the weakened boss.
Clean Up Safely: If the boss survives with low HP, finish it using long-range attacks from safe distances rather than sending wounded units into close-quarters counter fire.

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Emily Johnson

Emily writes practical mobile strategy guides with a focus on resource planning, base progression, and the early decisions that shape a long-term account.