Who exactly is sending grace to the tarnished hero protagonist in Elden Ring is somewhat of a mystery. Although the answer seems to become clearer as certain parts of the Elden Ring story are unveiled - it's not exactly so straightforward. The Lands Between are part of a world filled with rival factions that all have their individual agendas, so it's not surprising that such a question is shrouded in a dichotomy.
[Warning: This article contains spoilers for Elden Ring.]
In Elden Ring, grace is used to help guide players to the Erdtree so that they might be able to rightfully claim the title of Elden Lord. There are many Sites of Grace scattered throughout the Lands Between that are used as resting spots to heal, level up, and do other various activities; Sites of Grace, once discovered, also become a point of fast travel on the map. There is also deep lore rooted with grace, and Elden Ring's Shattering war that happened long ago in the Lands Between, tainted the essence and made it inaccessible to all tarnished individuals. However, the protagonist in Elden Ring is tarnished but has access to the rare gift of grace that only the non-outcasts have, such as the shardbearing lords in each region. This means that someone with the power to harness grace sent it out as a beacon calling for help.
The two characters that are most likely sending the grace essence out to the tarnished protagonist are either Queen Marika or the Two Fingers. Queen Marika who was tricked and locked away by her husband, Radagon, wanted to be set free, which is why a tarnished is the best candidate to help her. But the Two Fingers are also close to the protagonist and has its reasons for helping the tarnished hero claim the Elden Ring and become Elden Lord.
Queen Marika Or Two Fingers Are Likely Sending Grace To The Tarnished
Elden Ring's story hints that Queen Marika is the one that originally sent grace to the resurrected protagonist to save her from Radagon. While there's nothing that confirms this absolutely, it's at least proven that she has the power to take away the gift of grace and turn individuals into tarnished. Upon resting at the Site of Grace in the Third Church or Marika in eastern Limgrave, Melina quotes Queen Marika from the past saying, "My Lord and thy warriors. I divest each of thee of thy grace." This was a quote from the moment she stripped her first husband, Lord Godfrey, of his role as first Elden Lord, and he subsequently became the first tarnished. Years later, however, after she's been locked away, she now wants help to break the curse she created for herself by granting the power of grace to a chosen tarnished.
The Two Fingers could also be responsible for sending grace out to the tarnished protagonist. Throughout Elden Ring's story, the Two Fingers give advice to the protagonist at the Roundtable Hold by having its Finger Reader interpret messages. It becomes clear that Two Fingers aren't a fan of the shardbearing siblings, and they want to bring order back to the Lands Between as it was before The Shattering when the Golden Order had purer intentions. The Two Fingers are a mysterious force that possesses deity-like powers, so it wouldn't be far-fetched to believe that it sent grace out to many different tarnished individuals in hopes that one would prove themselves and become Elden Lord; in return, the Two Fingers would be like what Queen Marika used to be earlier in Elden Ring's history.