Bone-shaking Thunder is a unique Level 4 Evocation Spell and a variant of Kereska's Favour that allows its caster to imbue themselves with the power of thunder and unlock resistances and spells associated with it. It is granted by Markoheshkir.
Description
Embrace Kereska's thunder to gain Resistance to Thunder damage. Your thunder spells deal additional Thunder damage equal to your Proficiency Bonus. When you deal spell damage, inflict 1 turn of Reverberation upon the target. While attuned to Kereska's thunder you can cast Shatter and Destructive Wave.
Properties
Grants the following:
- Rumbling with Kereska's Thunder status (
Duration: Until Long rest) - Can cast
and 
once each per Short Rest.