Can't get Fortify buff in delve

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(Fortifying grants an amount of Fortification based on the Damage of the Hit)

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Problem:
Fortify is intended as a defensive benefit for being a melee character, but can often be obtained by spellcasters using melee weapon types without engaging in melee combat.

Solution:
Change the Fortify mechanic so it is given as stacks of Fortification, which is gained based on how much melee damage you deal.

Specifics:
Sources of Fortify now grant a number of stacks of Fortification based on the percentage of the enemy's ailment threshold dealt by the hit that applied Fortify to you, with a large bonus to fortification stack generation against rare and unique monsters. You have 1% less damage taken from hits for each stack of Fortification, and Fortification lasts 5 seconds by default. Fortification from multiple melee hits or different sources stacks, up to a default cap of 20 stacks. You can only gain Fortification stacks from one hit every 0.1 seconds.