I see it gives the attached character every trait

Does that mean it gets every single trait in the game? Like Lady, Lord, Dragon, Ally etc etc?

And how do you know how many traits there are?

I find this card very difficult to track as a new player since I dont have a list of all the traits.

How is this used by experienced players?

Also:

Why would you want to attach something to your house card? is that just so it cant be destroyed?

There is no list of traits at all that i know of, but as the harp gives EVERY trait then it makes the character a valid target for every trait based ability, want to be able to throw more dragons into challenges to trigger the queen of dragons rhagel viserion or drogon? The harp makes the attached character a dragon, so it dosent break the dragons responses, if you have the queen of dragons danny in play the attached character wont kneel to attack.

Or you could attach it to an opponents character and then use the trait abilities of daario and jorah from where loyalty lies, or the shadows varys, to discard them.

It is VERY scary and powerful with a bit of thought (more so as targ can recycle it quite quickly).

Attaching things to your house card, i assume you mean cards like khal drogos tent that would have the option of being a normal location?

In this case yes, its just a way to stop them being targeted by abilities that would remove locations, it does make them vulnerable to attachment removal though. cards like the long summer are still considered in play when attached to your house card (as the house card is considered in play itself) and thus can be targeted normally.

Hope that helps.

Yup that sums it up thanks!