Contract of Non-Agression

Flash, indestructible, hexproof.
When you cast it, alert everybody on your table.
After that, opponents may sign up the contract.
Opponents who signed up the contract may not
attack you or target you with spells, and vice versa.
This rule doesn't spread on permanents.
If the treaty is broken by somebody but you,
tell the person attacking you to stop.
If they say no, delete their name from the contract.
If this treaty is broken by you, sacrifice it.
If there are 2 players on the board, sacrifice