Does Sona's triggered ability trigger only when she is at a battlefield, or does it trigger every end of turn regardless of location?

Ruling: Sona's triggered ability only triggers when she is at a battlefield. The "while" at the start of her ability text creates a passive condition that must be met for the trigger to be active.

Nuances:

• The "while I'm at a battlefield" clause is treated as a passive ability that conditionally gives Sona the triggered ability, rather than being part of the trigger condition or resolution effect
• This can be understood as: "While I'm at battlefield, I have 'Ready up to 4 friendly runes at the end of your turn'"
• The positioning of "while" at the start of the sentence makes it function differently than an "if" clause that appears after the trigger condition
• The CR explicitly states she doesn't trigger when not at a battlefield