Tengu format ruling
Harpie's Pet Baby Dragon

Card effect (current official text)This card gains effects based on the number of "Harpie" monsters you control, except "Harpie's Pet Baby Dragon".
● 1 or more: Your opponent cannot target "Harpie" monsters you control for attacks, except "Harpie's Pet Baby Dragon".
● 2 or more: Double the original ATK and DEF of this card.
● 3 or more: Once per turn: You can target 1 card your opponent controls; destroy that target.
Rulings
- These effects accumulate, so if you have 3 "Harpie Lady" on the field all 3 effects are applied. Only face-up Harpies count, though.
- If you activate the 3rd effect of "Harpie’s Pet Baby Dragon" and the opponent chains an effect to destroy 1 of your other "Harpie" monsters, leaving you with only 2, the effect still resolves properly because the conditions were correct when it was activated.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Tengu forum — sourced change requests get reviewed.