I'm a fairly new DM and I made the huge mistake of going all homebrew on my first campaign. I tried running LMoP with it, but it went pretty bad and we decided to just play D&D 3.5e instead.

However, the players are already in Phandelver, so I'd like to play the story out, but what about the mechanics and monsters?

I figure I just replace things like athletics checks with a jump/climb/swim check and so forth, but can I keep the DC's roughly the same?

Can I replace the monsters with their 3.5e version? Should I replace them with something with the same CR? I'm especially worried about the dragon.

And finally, are there any other looming problems that I'm completely missing right now?

I can find a lot of resources and tools on converting 3.5e to 5e, but not the other way around. Any help or pointers in the right direction would be greatly appreciated!

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    \$\begingroup\$ Is there a reason you are switching from the homebrew system to 3.5e instead of just switching to running Phandelver with the included 5e rules? \$\endgroup\$ Jan 18, 2016 at 16:25
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    \$\begingroup\$ @SevenSidedDie I asked my players whether they wanted to play 3.5e or 5e and there was an overwhelming preference for 3.5e \$\endgroup\$
    – Berry
    Jan 18, 2016 at 18:39

1 Answer 1


The difference between 3.5e and 5e mechanically - are pretty great. Particularly as 5e introduces the "advantage / disadvantage" mechanic, which doesn't really have a close equivalent in 3.5e (yes, the Luck domain power can let you reroll a d20, and there's some other d20 trickery around as well, but it isn't really the advantage / disadvantage mechanic).

On page 3, LMoP says that DC10 is Easy, DC15 is Moderate, and DC20 is Hard. That's fair, and should work fine in both 5e and 3.5e. However, as you're going towards 5th level with the player characters (LMoP is meant to go from 1st to 5th, roughly), you may see that 3.5e increases in a different way as compared to 5th edition.

A 5th level 3.5e character can be expected to hit a bonus of about 10 - 15 pretty easily in a class skill, (+2/+3 from attribute, 8 ranks, perhaps a Synergy +2 and a Misc +2) and will therefore start hitting higher DCs consistently as compared to a 5th level 5e character. At 1st - 3rd level, I'd say the difference between 3.5e and 5e when it comes to DCs, is largely something you can ignore.

Goblins are goblins. Replacing them should be fine. Treasure is treasure - but I should also caution that I find 3.5e is more item-driven than 5e, so you should take a stock of things when LMoP is done, and perhaps up the treasure slightly at 4th and 5th level (slightly more potions, perhaps a scroll or two more, maybe slightly more powerful arms and armor).

Not that monsters - in particular undead and plant-based monsters - have different immunities in 5e as compared to 3.5e. The humans and orcs can be used much as they're written up in the module; you don't really need to do much there at all. Same goes for the ogre, and most other humanoids in the list.

I suspect the immunities and resistances of the dragon are quite different as well - but it's not an immediate issue, and you can look at it when you get there.

Attack bonuses start diverging once you level up a couple of times as well, but for NPCs it doesn't really matter much between 1st and 5th level. For NPCs of higher HD, you might want to recalculate attack bonuses though, based on their BAB and so on, in order to keep things challenging.

XP is a bit of a sore point. If the party starts lagging behind the suggested power curve, make sure that you're giving out enough XP. Also, consider giving out bonus XP (a hundred here, a couple hundred there) for particularly good and/or entertaining roleplaying. An RPG session shouldn't be death by spreadsheet - it should be fun, whichever system you're using.

So in short - yes, you can keep the DCs as suggested, you can keep the monsters pretty much as suggested, but you need to look at resistances and immunities, and towards the higher bracket you need to look at attack bonuses. You should also keep an eye on the treasure given (and possibly increase it), and if the party starts lagging behind you should consider upping the XP given.

Answer by SenseiZarn (link to comment on Reddit)

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    \$\begingroup\$ This is a lot for a quotation. Could you use your own words with quotes where it's particularly relevant? Otherwise this answer will likely end up deleted. \$\endgroup\$
    – wax eagle
    Jan 19, 2016 at 21:58
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    \$\begingroup\$ Even better would be writing up in your own words your practical experience doing it after running Phandelver in 3.5e, based on this advice (with credit of course), to advise others who might wish to do the same. Advice from experience is much better (and often different in unexpected ways) than advice from just intellectually considering a problem. \$\endgroup\$ Jan 19, 2016 at 22:13
  • \$\begingroup\$ I will write up an answer based on my own experience once the adventure is over. \$\endgroup\$
    – Berry
    Jan 21, 2016 at 10:29
  • \$\begingroup\$ @Berry Is your own adventure over now? Please provide an update so others can know how things went, and what you did. Or what didn't work and/or if/why it failed. \$\endgroup\$ Jun 2, 2019 at 14:22

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