Group size estimator

How many trainers do I need to invite?

The Estimator is already "trainers of this attacker needed to finish inside the timer", so this page does not invent a number: it reads it off the boss's own ranked counter list for three realistic parties and re-simulates each of them at every level from 20 to 50.

Raid bossTierIVsWeatherFriendshipDodgingShadow attackersMega attackersLegendary attackers

Invite 6 to be safe — 5 if everyone is prepared

At level 40, a party of Arceus (Dark)'s top six counters needs 4.14 trainers (round up: 5), and a mixed lobby of ranks 13-24 needs 5.17 (round up: 6). The raid timer is 300 seconds and one prepared trainer alone would take 19:03. No level in this range makes it soloable with a prepared party.

Arceus (Dark) · Elite

dark

Weak to

fightingbugfairy

Boss CP: 56,910
Boss HP: 20,000
Raid timer: 300s
Party used: 6

Trainers needed, by attacker level

Scroll sideways for the mixed-lobby column.

Trainers needed to beat Arceus (Dark) at each attacker level
Attacker level	Six of the best counter	A prepared party	A mixed local group	Prepared solo time	Faints per timer
Level 20	7(6.50)	7(6.57)	9(8.26)	30:13	6.0
Level 25	6(5.34)	6(5.47)	7(6.95)	25:10	6.0
Level 30	5(4.08)	5(4.68)	6(5.85)	21:33	6.0
Level 35	4(3.62)	5(4.38)	6(5.52)	20:09	5.9
Level 40	4(3.46)	5(4.14)	6(5.17)	19:03	5.9
Level 45	4(3.39)	4(3.96)	6(5.01)	18:13	5.9
Level 50	4(3.32)	4(3.84)	5(4.84)	17:41	5.9

Whole trainers in bold, the raw estimator in brackets — 2.04 means two trainers is right on the line and three is comfortable.

Six of the best counter

Every trainer brings six copies of the single best counter — the theoretical floor.

4 trainers at level 40

Keldeo3.46

A prepared party

Each trainer brings the boss's top six counters, powered up and correctly TM'd.

5 trainers at level 40

Keldeo3.46
Kartana4.08
Lucario4.14
Terrakion4.18
Zacian (Crowned Sword)4.37
Zamazenta (Crowned Shield)4.59

A mixed local group

Ranks 13-24: reasonable but unoptimised parties, which is what a public lobby usually is.

6 trainers at level 40

Conkeldurr5.08
Eternatus5.11
Marshadow5.13
Enamorus (Incarnate)5.32
Genesect5.16
Genesect (Burn)5.16

The party these numbers assume

1. Keldeo

Low Kick + Secret Sword

2. Kartana

Fury Cutter + Sacred Sword

3. Lucario

Force Palm + Aura Sphere

4. Terrakion

Double Kick + Sacred Sword

5. Zacian (Crowned Sword)

Metal Claw + Play Rough

6. Zamazenta (Crowned Shield)

Metal Claw + Behemoth Bash

See the full ranked counter list for Arceus (Dark) · check a real lobby (win chance, who brings what) · make a share card of the top six

How this is worked out

The boss is ranked once at level 40 with rankCached (the same memoised call /raids makes), then the three bands — rank 1, ranks 1-6, ranks 13-24 — are re-simulated at each attacker level with an 8-run Monte Carlo each. Holding the party fixed and moving only its level is deliberate: it answers "what if my party were level 20" rather than "what would a level-20 player's completely different party be", and it is about ten times cheaper than re-ranking every attacker seven times. The Estimator itself is Pokebattler's definition, time to win including rejoin time divided by the raid timer.