At the next end of your opponents turn, delete it
If you want to maximize Library, lean hard on early interaction, free spells, and powerful acceleration, which is basically what you want anyways (and therefore is something everyone is competing for)
Since monsters sent to your partner will earn your team 500LP regardless of their actual stats, its a good idea to send weaker monsters to your partner to get as much out of them as possible
Anytime you have Ursula sing a song, you can then play that card again from your discard pile for free
this card gains 1000 ATK/DEF until the end of the Battle Phase
each player sends the top 4 cards from their Deck to the GY, then if any monsters were sent to either GY by this effect, you can Special Summon 1 of those monsters to your field