Adamantine tarrasque scale Vampire coffin

Legendary Wonderous item
Ac: 23 Hp:40 Hardness: 20
Immunity to force,fire, Nonmagival BPS
Any time the coffin is targeted by a magic missile spell, a line spell, or a spell that requires a ranged attack roll, roll a d6. On a 1 to 5, the coffin is unaffected. On a 6, the coffin is unaffected, and the effect is reflected back at the caster as though it originated from the coffin, turning the caster into the target.
any critical hit against coffin becomes a normal hit.
When person or vampires misty form enters coffin locks from inside forcing coffin to be busted open before can stake those inside.