Avalon, Everdistant Utopia

Flash, Indestructible, Hexproof
If Avalon would be put in exile or graveyard, you
may shuffle it into your library instead.
Prevent all damage that would be dealt to you.
Sacrifice Avalon: Target creature cannot leave
the battlefield this turn. If that creature is named Artoria or Arthur, put four +1/+1 counters on
them.