While “Royal Decree” and “Talisman of Spell Sealing” are both active, and “Sealmaster Meisei” is removed from the field, “Talisman of Spell Sealing” stays on the field, but if “Royal Decree”’s effect is no longer being applied, “Talisman of Spell Sealing” is destroyed.
“Talisman of Spell Sealing” is destroyed immediately when “Sealmaster Meisei” is not on the field. If your opponent chains “Ring of Destruction” to “Talisman of Spell Sealing” to destroy “Sealmaster Meisei”, “Talisman of Spell Sealing” is immediately destroyed when “Ring of Destruction” resolves.
If you have “Talisman of Spell Sealing” and “Talisman of Trap Sealing”, the controller can select which effect will be applied. If both players have both, the turn player chooses which effect is applied