Potty Games - Riddles Only (Vol. II)

Polyjuice Potion! Congratulations!

Some explanation is in order, I think.

Most of the riddle refers to the list of ingredients for Polyjuice Potion.

Three times seven without flight
Lacewing flies stewed 21 days - I suppose they don't fly when they are stewed. Flight - fly - by association.

When the moon is full and bright
Fluxweed picked at full moon.

Something like this can be tied
Knotgrass - you can tie a knot (or the knot ).

What was two now multiplied
Powdered bicorn horn - 'bicorn' suggests a creature with two horns. When powdered, it consists of lots of small parts.

Feeding with persistent greed
On the thing that all hearts need
Leeches, which suck blood.

Lost and found, stolen and used
Shredded boomslang skin - Snakes lose their skins, but someone must find them if they end up in the possession of wizards. Boomslang skin was stolen from Snape's office by Hermione and then used by the Trio in their potion.

(Many found themselves confused)
Reference to the little diversion Harry created in their potions class so that Hermione could go into Snape's office.

To crown it, you need one more
A bit of who one wants to turn into is added last.

Nothing will be like before
Change: the effect of Polyjuice Potion.

Whatever you want to gain
Remember Cinderella's bane
Cinderella had to leave the ball at midnight, because then the magic was over and everything changed back to normal. Likewise, if you take Polyjuice Potion, you must remember that the effect of a single dose wears off in an hour.

Hint: The first one was for the worse and marred by an unfortunate mistake.
The first use of Polyjuice Potion in the books was a change "for the worse" because two good guys (Harry and Ron) changed into two bad guys. The unfortunate mistake was the one with the cat hair, which sort of spoiled the experience for Hermione.

Guessed: the Potter family, Bill Weasley, Buckbeak, Grawp.

The answer to the riddle is The Sign of the Deathly Hallows.

First one of a name fair
The 'fair' name is Albus, which means white. Dumbledore used the sign instead of the initial A in his name, in his letter to Grindlewald.

Caused this seeker to stare
The seeker is Krum, who was astounded when he saw Xenophilius wearing the sign around his neck.

On a grave,
We see the symbol on the gravestone of Ignotus Peverell.

and in books
On clothes, to get looks
Krum says, "Some idiots copied it onto their books and clothes thinking to shock, make themselves impressive..."

I keep cropping up everywhere.
The trio keep encountering the symbol throughout the Horcrux Hunt.

Hint: I cause to stare but I can't stare back, despite appearances.
The symbol is described as a triangular eye, but of course it can't really see.

Guessed: Gryffindor's Sword, Snape, Bloody Baron, Godric Gryffindor, Aragog.