During your main phase, if your current vanguard is not and was never in legion state, and your opponent has a grade 3 or greater vanguard, you may choose four cards from your drop zone, and return them to your deck in any order.It is indicated on the legion leader by the icon 'Legion(number)', for example ' ', and followed by one or two card names marked in red, indicating the legion mate to search for. The 'Seek Mate' (シークメイト Shīkumeito) ability allows you to get the 'legion state'. It is then placed on the left of the vanguard circle while the Legion symbol expands and fades. The same sparkles then glow, usually from the top to the bottom of the deck, and the Mate is ejected out and caught by the fighter when it is found by the sparkle. The scene then cuts to the table, where four cards are moved from the drop zone to the top of the deck. In the anime, Legion is activated by the fighter declaring 'Seek (the/my) Mate!' a yellow aura glows from the Legion Leader, and rises up in the sky, where it sparks. There are some cards that do not follow this, usually cards released before the era of Legion and later gained their Legion Leader.

Many pairs of Legion cards appear with a shared artwork side by side, each having the half of the Legion symbol in a corner of the card layout. It appears as an icon of two crossed swords with ' 双闘レギオン'/'Legion' written over them: /. It was introduced in the Trial Deck 14: Seeker of Hope and Trial Deck 15: Brawler of Friendship. 'Legion' ( 双闘レギオン Region) refers to the state where two units are on the vanguard circle side by side, usually due to the keyword 'Seek Mate'.

Pale moon vanguard legion