A contraceptive herb. The Tesslas plays (Young Tesslas, Brave Tesslas, Tesslas in chains) were plays performed in-game and contained hints about cosmic happenings being leaked to mortals by a renegade cosmic. PC's knew because costume and sets were loaded with secret symbols of their order but actors an set design just said the writer designed them, they couldn't find the playwright (was possible, they just failed) but they found and read an interview he gave that said he was inspired by dreams and didn't understand everything in his own plays. Since Maryn discarded the abortion stuff, it meant that she bore Tesslas's child between the 2nd and third plays (15-20 year gap) which in turn means the sun god, who Tesslas represented, got the rain goddess pregs for reals but it's super secret or else the baby will get confiscated/ corrupted. Inspiring a playwright to send coded messages unknowingly was a good way to sneakily tell only certain mortals. Direct communication is "bugged" but the evil gods don't dig through every bit of minor inspiration looking for hidden meaning.