Constitution

[DARKJAY]

Rulebook says:

Stacking Spells

A spell recipient cannot benefit from two or more of
the exact same spell. Spells cannot be “stacked” if
they are the same spell, but spells that are similar can.
A Resistance granted by a spell can be stacked with
the same Resistance from another source. For
example, a Deep Gnome’s racial Resistance to Earth
spells can be stacked with the spell Earth Resistance.