Thalassa's Necklace

You may pay {u}{r} rather than the mana cost to activate the ability of Thalassa, Storm's Captain.
Whenever you are dealt combat damage you may shuffle this card into your library.
If you do, deal 3 damage to any target.
The crystal connects her to something mystical.
I shudder at what she would do if it were ever lost.
- Malcolm, Keen-Eyed Navigator