Is there a free browser MMO with 20 v 20 battles between players?

Yes: in Heraldmoor Online, a free medieval MMO in your browser, players hold arranged battles from 1 v 1 up to 20 v 20: last side standing in the Thornwall Lists, or a fight to hold the standard on Kempfield, the great battlefield. Nobody loses their things, and up to 50 players can watch.

A free browser MMO with 20 v 20 battles between players

Two grounds

Small battles, up to 5 a side, are fought in the Thornwall Lists, the fenced tourney ground beside Thornwall Castle: the last side standing wins, within five minutes. Bigger battles, 6 to 20 a side, are fought on Kempfield, an enclosed field on the east coast with a camp at each end. The two sides fight under red and blue. A standard stands on a mound in the middle, and its banner takes the colour of whichever side holds it. Each moment a side holds it scores a point, and four minutes of holding wins. Anyone struck down is carried back to their camp and fights on 15 seconds later. If neither side has won after ten minutes, the side with more points wins.

Kinds of battle

A public battle is open to anyone, and the game finds players for it, starting with those nearby. A private battle is by invitation: you lead one side and name a rival captain to lead the other. In a same-kit battle everyone fights in the same steel kit, while their own bag and armour are held safely and handed back afterwards. A boss battle takes a band of up to five to one of the bosses' lairs.

The purse

The host can set an entry fee, paid in credits, which you buy with coins at one coin each. The winning side shares the purse. A draw, or a battle that is called off, gives every fee back. No battle ever costs you your items.

Getting in

Talk to the Herald of Arms beside the notice board in Millhaven, Thornwall or Moorwick, or tap Battles in the menu, from anywhere. Quick battle puts you in an open battle of the size you pick. Before a battle starts, everyone has 15 seconds to tap Ready. A hall of fame keeps the most wins, the most knock-outs and the greatest battles.

How to start

Open Play now in your browser.
Pick a name, choose how your character looks, and you’re in Millhaven, the capital, across the market square from the King’s castle.
Tap Battles in the menu, or talk to the Herald of Arms beside Millhaven’s notice board, and pick Quick battle or Hold a battle.
To keep your character, add a password in Settings, then Account.

At a glance

Price: Free to play. Nothing in the game is sold for power.
Plays on: Any up-to-date web browser: iPhone, iPad, Android phones and tablets, Chromebook, Windows and Mac.
Download: None. You can add it to your Home Screen for a full-screen app icon.
World: 288 × 672 tiles: the safe Kingdom with eight towns and villages, the Southmarch below it with Wardbury, the King’s muster field, the Wildlands across the middle where players can fight, and the frozen Hoarfells in the far north, with the richest resources and a single hamlet.
Combat training: Wardbury’s drill yard, 5 minutes’ walk from Millhaven: pells, dummies, a quintain, archery butts and a sparring ring, with monsters graded by distance all round it.
Skills: 13 to level: Attack, Strength, Defence, Hitpoints, Archery, Woodcutting, Mining, Fishing, Cooking, Smithing, Fletching, Firemaking, Leatherworking.
Horses: Every player can claim a free horse at the Royal Stables and ride it anywhere, 12 coats to choose from.
Adventure: 5 story quests, 3 boss fights for 1 to 5 players, and a town raid every weekend.
Pace: The world moves in 0.6-second ticks, the steady rhythm of classic tile-based MMOs.
Players: One shared world: trade face to face, duel, group up, chat and meet at weekend events.
Voice chat: Proximity voice chat: hold the voice button and players near you hear you, louder the nearer they stand. Off until you turn it on.