As Jeff pointed out in his Heroquesting posts, a crucial step is "Identification". So according to the character runes, which character/deity will he identify with? It will not be a thunder brother, sword, Axe Bearer, etc. For example the character of Vasana has the following runes: Air 90% (air does not exist yet); Death 75% (death does not exist yet); Earth 20% (OK); Movement 75% (OK), Truth 70% (OK). So the identification may be done on these three runes. So Earth: phylum --> reptile; organs: genitals, bones. This is the basis for determining identification. Movement: changeable, energetic, rebellious, ambitious. Truth: objective, the torch of truth. The result must be something strange to destabilize the player. The GM declares that the character identifies with the Three-Tailed (Movement) Snake (Earth) Guardian of Sexual Truth (whatever it is). Yanioth: Earth 90%, Beast 85%, Fertility 85% so OK Identification with young earth goddess, not a big change). Etc.
Yanioth will probably come back with the knowledge of a new myth about the goddesses of the earth, new rune spell/power related to Fertility. For Vasana, this could imply a more significant change (related to the Sexual Truth?).
I suspect that the danger is greater for characters like Vasana than those like Yanioth