Tengu format ruling
Ritual Weapon

Card effect (current official text)Equip only to a Level 6 or lower Ritual Monster. It gains 1500 ATK and DEF.
Rulings
- The equipped monster's current Level needs to be 6 or less, not original Level.
- If the equipped Ritual Monster's Level is increased to 7 or more, Ritual Weapon is destroyed.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Tengu forum — sourced change requests get reviewed.