Polymorphic Titan

By assuming the form of a less powerful creature, you can dramatically extend the duration of your transformations.

17th level, you know the polymorph spell as a 6th-level spell, and you have at least one Huge predetermined polymorph form.

When you cast polymorph on yourself as a 6th-level spell to transform into a Huge predetermined form, you can spend 1 RP to transform into a Gargantuan version of that form instead. The Gargantuan form grants a +4 enhancement bonus to Strength-based ability checks and skill checks. Alternatively, you can spend 2 RP to instead transform into a Colossal version of that form with a space of 30 feet, granting you a +5 enhancement bonus to Strength-based ability checks and skill checks.