Rule 902.4 · Vanguard
Each player’s starting life total is 20 plus or minus the life modifier of their vanguard card.
Example: The life modifier of a player’s vanguard card is -3. That player’s starting life total is 17.
Ask the judge Pro
The life counter has an AI judge that answers your play citing the exact rules. It is part of Gatewatch Pro; the rules, Oracle text and rulings stay free.