Tiny Leaders

Tiny Leaders is a Magic: The Gathering format. Although not officially santionable by Wizards of the coast it is popular with casual plaers. It is a singleton format that uses a Commander and restricts deckbuilding to cards of converted mana cost 3 or less. 

It was conceived in 2013 and has its own list of banned and restricted cards.

Rules

• All cards must have a converted mana cost of 3 or less.
• Each player chooses a legendary creature (or suitable Planeswalker) which is their commander. Decks may use other legendary creatures as well. Partner commanders are only legal if their combined color identities are less than four total colors.
• Decks must have a color identity that is a subset of the color identity of their general. The color identity of a card is composed of every colored mana symbol that appears on that card — whether in the mana cost or the rules text.
• Except for basic lands, players may not use more than one copy of any given card unless stated otherwise on the card itself.
• Each deck must contain exactly 50 cards including the General, and may additionally have a sideboard with a maximum of 10 cards
• Players start with 20 life.
• Each player's starting hand size (before mulligans) is 8 minus the number of cards in their command zone (meaning 7 cards for regular commander or 6 cards for Partner commanders).