Union Arena Slime Deck Guide: Green Milim Build 2026

Union Arena Slime deck guide time: Green Milim has stayed a real, community-discussed archetype since UE20BT launched, even without a headline regional finish of her own yet. This guide covers the actual printed card text behind her Raid-and-Snipe engine, the cheaper Demon Lord support piece backing her up, and where the honest gaps in tournament data currently sit.

TL;DR: Green Slime runs on Milim (UE20BT/TSK-1-085, 8-cost, 5000 BP), a Raid Character whose When Played ability sidelines an opponent's site and grants herself Snipe (unblockable single-target attacks) for the turn, then chooses Impact or Damage 3 on her next attack. A cheaper Milim (UE20BT/TSK-1-084, 6-cost) backs her up as Demon Lord affinity support, with Damage 2 and a BP boost on entry. Green Milim shows up in real community matchup discussion, though it hasn't logged an official regional placement the way some other current Union Arena archetypes have.

What does the Union Arena Slime deck actually do? (quick answer)

Raid Milim in, strip a site from the opponent's field while making her briefly unblockable with Snipe, then pick between bonus combat damage or a bigger direct-damage swing on her next attack. It's a tempo-and-reach deck built around one expensive, flexible bomb rather than a wide board of small threats.

Overview: Milim's Raid-and-Snipe engine

Milim (UE20BT/TSK-1-085, SR) is an 8-cost Green Raid Character with 5000 BP and the Demon Lord affinity tag. Her When Played ability does two things at once: she sidelines one of the opponent's sites, and she gains Snipe until the end of the turn, meaning she can target a specific character on the opponent's front line and attack it while the opponent can't block. That combination removes a resource and threatens a clean hit in the same turn.

Her When Attacking ability adds a second layer of flexibility: choose between granting herself Impact ① (bonus damage on a won battle) or Damage ③ (tripled direct damage) until the end of the turn. Impact rewards a turn where she's likely to win a straight fight; Damage rewards a turn where she can connect unblocked, which her own Snipe ability from the same turn often sets up directly.

Milim's When Played ability: sideline an opponent's site and gain Snipe, setting up an unblockable hit the same turn she enters.

GODEEPER: New to Union Arena's Raid mechanic entirely? The full rules breakdown covers how Raid Characters work across every color, not just this one. Union Arena Raid Mechanic Explained →

The cheaper Milim: Demon Lord affinity support

Not every Milim card in this deck is the expensive Raid bomb. Milim (UE20BT/TSK-1-084, R) is a cheaper 6-cost Character at 4000+ BP that plays a completely different role: affinity payoff rather than finisher.

Her printed condition lets her enter play set to active outright once you already have five or more other Demon Lord affinity cards on your field, a real reward for committing to the tribal plan rather than splashing Milim as a lone bomb. She also carries Damage ② (tripling direct damage to 2) and gains 1000 BP When Played until the start of your next turn, useful stats on a body that's often coming down for free off the affinity condition.

The cheaper Milim rewards a genuine Demon Lord affinity board rather than acting as a second copy of the expensive Raid finisher.

Step-by-Step: piloting Green Slime

1. Build toward the 5-card Demon Lord affinity threshold before relying on the cheap Milim's free-entry condition. Playing her before that board state is met just makes her a normal 6-cost play, not the free tempo swing her text promises.

2. Time Milim's Raid entry around a site worth sidelining. Her When Played ability is a real tempo swing only if the target site actually matters to your opponent's plan that turn.

3. Choose Impact or Damage on her attack based on what actually closes the turn out. Impact rewards a fight she's favored to win outright; Damage rewards a hit that's already unblockable thanks to her own Snipe.

4. Don't treat Snipe as a permanent keyword. It only lasts until the end of the turn she's played, so plan the attack that uses it in the same turn, not the turn after.

Tips

Read Milim's Damage keyword numbers carefully before assuming both cards do the same thing. The cheap Milim (084) carries Damage ②, while the expensive Raid Milim (085) grants herself Damage ③ as an attack option, a real difference in a close race.

Community discussion has paired Green Milim against builds like Purple Saito in casual matchup content, useful context for what the deck is actually expected to face at a normal table, even without a formal tier list entry yet.

If you're building around the cheap Milim's affinity payoff, count your actual Demon Lord-tagged cards before assuming the threshold is easy to hit. Five OTHER cards on the field at once is a real board state to build toward, not an incidental byproduct of a normal curve.

Because the UE20BT set spans three anime seasons and four colors in one release, it's worth checking which supporting cast members outside Milim herself also carry the Demon Lord affinity tag before finalizing a 50-card list. A deck that only runs Milim's own line and hopes to hit five affinity cards purely off her copies will struggle to reach that threshold consistently; the payoff assumes real affinity density across your whole build, not just a handful of named Milim prints.

Where Slime actually stands right now

Union Arena's official top-placing decks archive doesn't yet show a headline regional result for Green Milim the way it does for Bleach, Rurouni Kenshin, or several other current archetypes. That doesn't mean it isn't played: community deck-tech and matchup discussion treats it as a real, currently-active build worth knowing how to play against, even without an official placement to cite yet.

GODEEPER: Curious how the rest of the current Union Arena field is doing by comparison? Union Arena Current Meta: Which Deck Is Strongest Right Now →

Key Takeaways

• Milim (UE20BT/TSK-1-085, SR, Green, 8-cost) is the deck's Raid finisher: her When Played ability sidelines a site and grants Snipe, then her attack trigger chooses Impact or Damage 3
• Milim (UE20BT/TSK-1-084, R, Green, 6-cost) is a cheaper Demon Lord affinity support piece that can enter play set to active with 5 or more other Demon Lord cards on the field
• The UE20BT set spans anime Seasons 1 through 3, a wider content window than most single-cour Union Arena releases
• Green Milim is a real, community-discussed archetype without an official regional placement logged yet
• Snipe only lasts the turn it's granted, so the unblockable attack window is a same-turn plan, not a standing keyword

Frequently Asked Questions

Is Green Milim a good deck in Union Arena? It's a genuine community-tracked build, cited alongside decks like Purple Saito in casual matchup discussion, though it hasn't logged an official top-placing regional finish the way Bleach or Rurouni Kenshin have. Treat it as a real, currently-played option without an official result to point to yet.

What does the Milim SR card actually do? Milim (UE20BT/TSK-1-085, SR, 8-cost, 5000 BP) is a Raid Character. When Played, she sidelines an opponent's site and gains Snipe for the turn. When Attacking, she chooses between Impact 1 or Damage 3 until the end of the turn.

What is the cheaper Milim card for? Milim (UE20BT/TSK-1-084, R, 6-cost, 4000+ BP) is a Demon Lord affinity support piece. She can enter set to active with 5 or more other Demon Lord cards on the field, carries Damage 2, and gains 1000 BP When Played.

Does Union Arena's Slime set cover the whole anime? Yes. The official UE20BT product page confirms the set spans Seasons 1 through 3 of the anime, a wider window than most single-cour Union Arena releases.

Is this a good deck for new Union Arena players? It's approachable but the Snipe and Damage keyword interactions take a game or two to read correctly, since they change how blocking and direct damage work on a given attack. A simpler top-tier deck is generally friendlier for a first Union Arena deck.

Related Reading

• Union Arena Tokyo Ghoul Deck Guide: Purple Kaneki 2026: Another archetype without a headline regional result yet, but a genuinely playable current build.
• Union Arena Card Rarities Explained: Every Tier in 2026: What SR and R rarity actually mean for cards like Milim's two prints.
• Union Arena TCG Beginner Guide: How to Start (2026): The sites, sideline, and energy basics behind every card in this guide.
• Union Arena Deck Building Guide: Build a 50-Card Deck: The construction rules to apply once you've picked this archetype.

References

• UNION ARENA SPECIAL BOOSTER PACK That Time I Got Reincarnated as a Slime [UE20BT] official product page: Bandai's official set listing and release details
• UNION ARENA Card List, official card database: Source for both Milim cards' verified text used in this guide
• TCGPlayer Union Arena: That Time I Got Reincarnated as a Slime: Card pricing reference