Vestrum of the Marcurian Sentinel at the time of TLJ, Tobias Grensret was the first person April met when she Shifted to Arcadia, arriving in the Temple of the Balance. He helped her to speak Na'ven and answered her questions. Tobias also told April the story of how the Balance was created, using the Murals of the Balance to illustrate what happened. When she returns, Cortez tells April that he knew Vestrum Tobias when he was just an Istrum.
Just before she set off on her voyage to Alais, Tobias told April she was the thirteenth Guardian (mistakenly, as it turned out) and gave her the Talisman of the Balance, which April uses several times.
Tobias is a gentle, intellectual man who spends most of his time in the Temple in Marcuria studying the histories of the Fathers, the Balance, and mudhoppers. However, as Minstrum Yerin sorrowfully tells April, Tobias is murdered in the temple at the climax of the game. The identity of his killer or the motive behind the attack is not known, but Yerin claims Tobias looked very peaceful when they found him, and that it was probably someone he knew.