Skip to main content
Community

Mongil: Star Dive Custos Boss Guide — Best Team, Strategy & Drops

First major dungeon boss in the launch progression. Custos is an Earth element guardian — weak to Ice, sits at recommended level 30, and serves as the difficulty introduction to the stagger-and-burst loop. F2P-clearable with any Ice carry and the launch SR support pair.

Custos Boss Guide — Best Team, Strategy & Drops

Custos
Mongil: Star Dive · Boss Guide

Custos Boss

Earth dungeon boss · Recommended Level 30 · 1.0 launch

First major dungeon boss in the launch progression. Custos is an Earth element guardian — weak to Ice, sits at recommended level 30, and serves as the difficulty introduction to the stagger-and-burst loop. F2P-clearable with any Ice carry and the launch SR support pair.

  • Boss
  • Earth
  • Weak: Ice
  • Lvl 30
  • HP 72k
  • F2P-clearable
How to clear it

Recommended approach

Custos is the first major dungeon boss in Mongil: Star Dive's launch progression — Earth element, weak to Ice, recommended level 30. HP sits at ~72,300 (modest by endgame standards) and the stagger gauge tops out at ~12,660 with a groggy DEF of 325. The Earth element means your usual Earth carries (Gabi, Ellie, Francis) lose most of their elemental payoff — Earth Affliction has no effect on an Earth-resistant boss. Build the team around Ice instead.

The clear pattern is straightforward: stack an Ice Brawler (Ophelia preferred) as the on-field carry, build the stagger gauge through her Special + Brawler-role Neutralization DMG, then dump damage during the groggy window. Cloud (SR Ice Destroyer ranged) provides Crystal stacking + Glacier Zone for the second damage line. Sera offers Freeze on Ult for an extended stagger phase — pull her in if you own her at C1+.

Pull-priority for this fight: any Ice carry works at level 30 — even SR-only teams (Cloud + Sera + Francis) clear it cleanly. The fight is designed as a difficulty checkpoint, not a wall. If you fail repeatedly, the issue is gear level (Equipment ~Lv25+ recommended) rather than team composition.

  • Story / first clearSDesigned as a launch difficulty checkpoint. F2P-clearable with Ice Brawler + Francis healer.
  • Conquest ticketsARepeatable for material drops. Stagger-focused Ice teams clear in ~90s once geared.
  • SpeedrunBModerate HP / stagger gauge ratio. Sub-60s clears require Ophelia C2+ or Cloud C1+ with optimal stagger timing.
  • F2P difficultySEasiest dungeon boss to clear F2P — SR-only Ice comp (Cloud + Sera + Francis) clears reliably.
  • Reroll filterCNot a meaningful reroll target — every comp can eventually clear it. Pull for later bosses instead.

Stagger windows

  • Stagger gauge ~12,660 — clears in 2-3 Special casts from an Ice Brawler with proper Neutralization DMG scaling.
  • HP only ~72,300 — fight ends in ~90 seconds once the groggy phase opens.
  • Earth element with single weakness (Ice) — clean elemental payoff, no element-locked phase shifts.
  • Groggy DEF only 325 — every team's burst window converts cleanly during stagger.
  • Recommended level 30 — accessible before the SR Conquest difficulty curve kicks in.
  • 10 HP phases — multiple stagger windows in a single fight, room to recover from a misplaced Special.

Boss threats

  • Hits all Earth Brawlers (Gabi, Mina-with-Fire-conversion ok, etc.) for reduced damage — Earth-element comps lose ~25% scaling.
  • Without an Ice carry, the fight feels grindy — Lightning / Wind / Fire only deal neutral damage (no elemental amp).
  • Stagger gauge does not auto-deplete — break it cleanly or the recovery (10s) resets your stagger build.
  • BIND animation type during groggy — limits team's mobility during the burst window, plan dodge windows around it.
  • Drop table is for crafting materials, not character shards — no pull-related rewards.
  • Solo (no co-op at launch) — single-character roster carries the fight.
How to clear it

Recommended team

Best counter carry, best team comp, and farmable alternates to clear Custos.

BIS counter carryBISOphelia (Ice Brawler)SSR Ice Brawler. Amethyst Witch buff loop + Subzero Verdict signature artifact converts her self-buffs into stagger damage. Cleanest single-character clear of Custos at C0 once Equipment ~Lv25+. If you do not own Ophelia, use Cloud (SR Ice Destroyer) as the lead.
Best team compBISOphelia + Cloud + FrancisLaunch SSR/SR Ice comp. Ophelia leads stagger, Cloud chips Crystal-stacked Rapid-Fire + Glacier Zone for second damage line, Francis heals through Drug Field + Earth Affliction. Earth Affliction from Francis is wasted on Custos (Earth boss), but her ATK-scaling heal still anchors survival. Replace Francis with Bonnie for the Wind Crit DMG buff if you prioritise burst over heal.

Alt team comps

  • Cloud + Sera + Francis (F2P SR-only) — Pure-SR Ice team. Cloud Crystal stacks + Sera dual-gauge + Freeze Ult + Francis heal. Slower clear than Ophelia-led but fully F2P-clearable at recommended level.
  • Ophelia + Sera + Bonnie (Ice + Wind support) — Double Ice melee + Bonnie's Encore (C2) team Crit DMG. Faster speedrun option if you own Bonnie at C2. Lose Francis healing — only viable at Equipment ~Lv30+.
  • Any Wind/Lightning team (off-element) — Functional but inefficient — no elemental weakness amp. Use if you have no Ice carry. Pair Bonnie + any Wind carry + Francis for the safe slow clear.
Fight mechanics

Custos at a glance

Stagger numbers, HP, and the elemental matchup — everything that matters for team-building.

Combat stats (in-game, level 30)

  • Element — Earth — neutralises Earth Affliction from your team.
  • Weakness — Ice — every Ice attack deals bonus damage; the Ice Brawler / Destroyer role is the lead carry.
  • HP — ~72,300 — fight ends in ~90 seconds once geared.
  • ATK / DEF — 275 ATK / 349 DEF — manageable damage output, modest defence.
  • Stagger gauge — ~12,660 / Groggy DEF 325 — breaks in 2-3 Special casts with an Ice Brawler.
  • Recommended level — 30 — gate the fight behind Equipment ~Lv25+ for a comfortable clear.
  • HP phases — 10 — multiple stagger windows in a single fight, recovery-friendly.
  • Stagger animation — BIND — limits team mobility during the groggy window, but does not punish dodge play.
Boss rotation

Suggested clear rotation

Five steps from entry to stagger dump. Adapt to your specific Ice carry's combo.

  • 1. Tag-In with the Ice carry (Ophelia / Cloud) — Open with the Ice Brawler's Tag-In attack — Amethyst Witch buff (Ophelia) or Frost Wave (Cloud) for AoE entry + initial stagger build.
  • 2. Special for stagger gauge — Ophelia's Subzero Verdict (Special) and Cloud's Piercing Ice (held + released for Crystal yield) both push the stagger gauge fast. Ice attacks hit Custos's weakness — every Special is a meaningful chunk.
  • 3. BA chain to maintain Ultimate gauge — Combo BA for Ult gauge generation. Cloud BA dumps Crystals via Rapid-Fire; Ophelia BA generates Amethyst Witch stacks.
  • 4. Trigger stagger → swap to your burst character — When the stagger gauge breaks, Custos enters BIND for ~Xs (animation timing). Swap to your highest single-instance damage character (Cloud Ult, Ophelia Subzero, Sera Ult Freeze) for the burst window.
  • 5. Repeat — Custos has 10 HP phases — Each phase opens a fresh stagger gauge. Build → break → burst, then position safely while the gauge recovers (10s). The fight rewards patient stagger management over button-mashing.
Loot

What Custos drops

Crafting materials, not character shards. Repeatable for the Ice gear path.

Drop table

Custos drops Earth-themed crafting materials used in the Green Nightmare set + Earth weapon upgrades. The exact drop list rotates with Conquest difficulty and is shown in-game on the dungeon entry screen — check the live dungeon panel for the current rotation rather than relying on a static list.

Repeatability

Custos is repeatable via Conquest tickets. Each clear consumes 1 ticket. The fight rewards material drops scaled to the Conquest difficulty tier — higher tiers drop higher-tier crafting materials. Prioritise this dungeon for early-game Equipment upgrade material farming.

Counter picks

Characters that counter Custos

Anyone Ice. Anyone with strong single-target stagger DPS. Avoid Earth comps.

  1. 1OpheliaOpheliaLaunch SSR Ice Brawler. Amethyst Witch buff loop + Subzero Verdict signature. The cleanest single-character clear of Custos at C0 once Equipment ~Lv25+.Ice · Brawler (SSR)
  2. 2CloudCloudF2P Ice Destroyer. Crystal-stack Rapid-Fire dump + Glacier Zone Freeze (with C1). Replaces Ophelia in pure-SR comps.Ice · Destroyer (SR)
  3. 3SeraSeraSR Ice Brawler. Freeze on Ult extends stagger windows for max team dump. Pair with Ophelia for double Ice melee.Ice · Brawler (SR)
  4. 4FrancisFrancisUniversal launch healer. Earth Affliction wasted on Custos (Earth resist) but ATK-scaling heal anchors survival regardless of element.Earth · Supporter (SR)

Ophelia + Cloud + Francis is the launch default. Switch Francis for Bonnie (Wind support) for a faster speedrun comp if you have her at C2.

Stop reading, start clearing

Plan the clear on ZeroLuck

Use these free tools to plan your team, browse community clears, and benchmark your stagger DPS.

Boss pageCustos boss pageFull data — stats, stagger numbers, drop table, dungeon entry.CommunityCustos clear teamsLive community teams running Ophelia or Cloud for Custos.MetaMongil tier listSee where the recommended Ice carries rank in the launch meta.
Quick answers

FAQ

What is the recommended level for Custos?
Recommended level 30. Equipment level ~Lv25+ is the comfortable clear threshold. Below that, the stagger gauge takes too long to break and you eat unnecessary damage.
What element should I use against Custos?
Ice. Custos is Earth element and weak to Ice — every Ice attack deals bonus damage. Earth attacks are resisted; Wind / Lightning / Fire deal neutral damage. Build the team around an Ice carry (Ophelia / Cloud / Sera).
Can I clear Custos F2P?
Yes, easily. The F2P SR-only comp Cloud + Sera + Francis clears reliably at recommended level. Even an Ophelia-only carry works once Equipment ~Lv25+ is reached. Custos is the launch difficulty checkpoint, not a wall.
How much HP does Custos have?
~72,300 HP at level 30. The fight typically ends in ~90 seconds with a geared Ice team. 10 HP phases break the fight into multiple stagger windows.
How do I break Custos's stagger gauge?
Stagger gauge is ~12,660 with groggy DEF 325. Ice Brawlers / Destroyers fill it fastest via Special skills. 2-3 Special casts from Ophelia or Cloud typically break the gauge. Use BA combos between Specials to maintain Ultimate gauge for the burst window.
Which character is best against Custos?
Ophelia (SSR Ice Brawler) is the cleanest single-carry clear. Cloud (SR Ice Destroyer) is the F2P equivalent. Sera (SR Ice Brawler) is a strong second slot for Freeze-extended stagger windows.
Should I bring Francis to fight Custos?
Yes, but her Earth Affliction is wasted (Custos is Earth resist). Francis's ATK-scaling Drug Field heal still anchors survival regardless of boss element. If you want to optimise for damage instead, swap her for Bonnie (Wind support, Encore +Crit DMG team buff).
What does Custos drop?
Earth-themed crafting materials used in the Green Nightmare set + Earth weapon upgrades. Drops scale with Conquest difficulty tier — repeatable via Conquest tickets for material farming. Check the in-game dungeon panel for the current drop rotation.
Does Custos have phases?
10 HP phases. Each phase opens a fresh stagger gauge that resets after recovery (10s if not broken). The fight is designed around multiple build-stagger → break → burst cycles rather than a single sustained DPS check.
Why are my Earth attacks doing low damage to Custos?
Custos is Earth element and resists Earth damage (75% incoming reduction — matches every other element except Ice which is 100%). Build the team around Ice instead. Earth carries (Gabi, Ellie, Francis Affliction) lose their elemental payoff entirely.

Sources & method

All stats and gauge numbers trace back to game data exports in games/mongil/data/boss-details/. Strategy notes are our editorial reading written in our own words.

  • In-game boss data — stats (HP, ATK, DEF), stagger gauge, groggy DEF, weakness matrix.
  • Dungeon entry data — recommended level 30, dungeonKey 20101, single-stage encounter.
  • Community team composition guide — Mongil: Star Dive launch comps.
  • Community clear runs — Ophelia / Cloud / Francis comp validation at recommended level.
Live community tools

Teams clearing Custos

Browse the community teams that have cleared Custos, preview them, or share your own team after a clear.

Content

Characters