One D&D character class in the Forgotten Realms unlocks its second form when it's "Bloodied"

Dungeons & Dragons 4th Edition (4e) continues its feature creep into D&D 5e. It all began when the boar showed up in the 5e 2024 Player's Handbook with the Bloodied condition. "Bloodied" simply means that a creature (player character, nonplayer character, monster, or what have you) has been knocked down to half its hit points. For the vast majority of creatures, being Bloodied is merely a narrative footnote. But for an increasing number of creatures, it's having a gameplay effect.

Take the aforementioned boar: When a boar is knocked down to half its hit points or fewer, it becomes Bloodied. When a boar is Bloodied, it begins rolling its attacks with Advantage. Having Advantage on your attacks means you roll with two 20-sided dice—instead of just one—and take the higher result. Advantage is awesome. Everybody loves it. There's never a time when you don't want Advantage. Unless you're volunteering to fail a Saving Throw or Ability Check, etc., and that's a whole other situation.

Suffice it to say, when that boar becomes Bloodied, it gets nasty. 

Now, thanks to the Forgotten Realms: Heroes of Faerun player expansion, there's a general Feat you can select, starting at Level 4, that makes you fight as nasty as that Bloodied boar: Purple Dragon Commandant.

Purple Dragons? There are Purple Dragons in D&D? Not exactly. There is a faction of warriors called the Purple Dragon Knights. Take the Purple Dragon Squire background. That gives you the Purple Dragon Rook feat. At Level 4, that feat (and/or Martial Weapons Proficiency) gives you access to the Purple Dragon Commandant feat. One of that feat's benefits is Last Stand. That benefit gives you advantage on attack rolls while Bloodied.

That's a lot of proper nouns, I know. And it's more straightforward than it sounds when I'm typing it out in a paragraph.

And if being a do-gooder Purple Dragon Knight doesn't sound like your cup of joe, then you're still able to access the Purple Dragon Commandant feat by having Martial Weapons Proficiency. So, it's probably not an easy get for dedicated spellcasters, but players dip into multiclassing builds all the time. 

Pretty awesome when you've got a feat that will make you fight harder, but also make you hold off on gulping that healing potion for one more round, or make your warrior tell the Cleric to heal somebody else on their turn.