D&D 5E Why are treants vulnerable to fire?

[Tequila Sunrise]

It's exactly as you say: people think of wood as fuel, so a creature made of wood ought to be flammable, right? Of course, anyone who's ever tried to start a campfire with a wet log (or even just a green one) has had a rather different experience.

Bingo. The bark is especially resistant to fire and temperature extremes. And seeing as how trees can't run away from fires like animals can, it shouldn't be much of a surprise that trees are more resistant than we are -- those that weren't went extinct a long time ago!

I think of it as, the treant actually has less hit points, but few things affect it much, and fire is one of those few things. You could instead give it half hit points and make it resistant to all but fire.

Still, fire shouldn't be any more effective against a treant than cold or swords or what-have-you. Heavy chopping blades (aka axes) might arguably be a candidate for 'the one thing that affects trees normally,' but the fact is that trees are tough mofos all around! (They have to be; see above.) So unless you explain treants as creatures that just happen to look like trees, rather than the sentient trees that they've always been, the fire vulnerability makes no sense.

 

[billd91]

In theory, you have to go back to Treants as monsters as presented across the editions. If they typically did not have vulnerability to fire, then why is it the case now. In the AD&D monster manual they are vulnerable to fire, but it was presented in a different fashion when calculating AC. That would not fly in 5E, because of bounded accuracy.

In 1e, they also suffer +1 damage/die for fire attacks.

 

[The Shadow]

This is the same intersection of rules and fiction that 3e tried to fix with dozens of rules, 4e fixed with "the rules always trump logic, ooze tripper" and 5e assumes DMs can sort out with a minute of common sense.

The first player who tries to starve a skeleton because "the stat block doesn't say immune to exhaustion" is getting laughed away from my table.

I grant that a little common sense on the part of the GM goes a very long way. And I grant that one doesn't need a bunch of rules for everything.

But in this case, all the tools are already present in the game, they just didn't use them. It would have been easy to add, "Immune to the frightened condition' to the stat block, but they didn't. It just strikes me as a lazy oversight.

 

[FitzTheRuke]

That's nothing. In the playtest Horses had low-light vision!

My wife (a horse person) laughed soooo hard.