Sentinel Dedication Feat 2

Source Pathfinder Player Core 2

You have trained carefully to maximize the protective qualities of your armor. You become trained in light armor and medium armor. If you already were trained in light armor and medium armor, you gain training in heavy armor as well. Whenever you gain a class feature that grants you expert or greater proficiency in any type of armor (but not unarmored defense), you also gain that proficiency in the armor types granted to you by this feat. If you have a class feature that grants you expert proficiency in unarmored defense and you're 13th level or higher, you also become an expert in the armor types granted to you by this feat.

Armor offers solid, reassuring protection in combat, and as someone who faces danger on a regular basis, you have made it your business to get the most out of your defenses. You stand solid on any battlefield, encased in the sturdiest armor you can find. When danger threatens, your solid defenses will safely get you, and hopefully your companions, home again. As a sentinel, you might be part of an order of knights or bodyguards who trained you how best to take advantage of heavy armor. On the other hand, you might just be an adventurer who took one too many grievous injuries and decided enough was enough, so you trained yourself to wear the heaviest plate you could get your hands on. Some witches or sorcerers have chosen to follow the path of the sentinel to increase their survivability. While this is less common, it's not less effective. Few will argue against stronger, heavier armor leading to a longer life, and as every turtle knows, it's always nice to have a nice hard shell to fall back on when threatened. No one has a tougher shell than a sentinel. Even in the midst of great battles, you know that your armor is your greatest ally. It won't abandon you, break, or falter as things get tough. You can rely on your armor to see you through whatever tough fights lie ahead, and the odds always seem better when you're protected.