Ways to Mess Up Enemies' Saving Throws?

[Fflewddur Fflam]

Besides spells like Bane and Contagion, and several conditions like Stunned, Paralyzed, etc., are there any other methods for negatively effecting enemies' saving throws?

[Gastronomie]

I think either the Monster Hunter (UA) or Battle Master had an ability that imposes disadvantage on concentration saves an enemy caster makes against the damage.

Otherwise… can't think up at the moment.

[Spiritchaser]

There's a sorcerer in UA who can summon snuggleguts the dire shadowhound,
There's a light cleric/theurge ability that I think qualifies
EKs get a melee attack that debuffs saves
Probably lots more

[hymer]

There's a sorcerer in UA

The regular sorcerer has Heighten metamagic to give disadvantage on saves, too.

[RickAllison]

Divination Wizard can drop a low roll for the enemy's save if the Portent die is low.

UA Theurge Wizard can increase the DC with Channel Arcana.

Certain magic items like Robe of the Archmagi and Rod of the Pact Keeper increase the DC as well.

[hymer]

Certain magic items like Robe of the Archmagi and Rod of the Pact Keeper increase the DC as well.

By that token, getting your casting stat set to 19 via magical item could help too, particularly if casting isn't your main shtick and you won't be investing in 20 in your casting stat.

[RickAllison]

By that token, getting your casting stat set to 19 via magical item could help too, particularly if casting isn't your main shtick and you won't be investing in 20 in your casting stat.

True, true. Especially for EKs wanting to drop some CC/AoE before cleaning up.

[JellyPooga]

Light Domain Cleric has Corona of Light (lvl.17), which inflicts Disadvantage on Saves vs Fire or Radiant damage.

Eldritch Knight has Eldritch Strike (lvl.10); Imposes Disadvantage on Saves after a successful weapon attack.

Ancients Paladin has Elder Champion (lvl.20); Disadvantage on Saves vs. Paladin spells/Channel Divinity within 10ft

Arcane Trickster has Magical Ambush (lvl.9); Disadvantage on Saves against your spells if you're hidden.

[fishyfishyfishy]

Doesn't the Diviner Wizard feature do something like replacing d20 rolls with some pre-rolled dice? If you have some low rolls I can see this coming in handy.

[Oramac]

If UA is allowed in your game, I assume regular homebrew is as well?

If so, the Death Knight in my sig focuses a lot on debuffing the enemy. Specifically, the 6th level feature that gives a debuff to enemy saving throws within range.

Other than that, all the stuff said here works too. The Divination wizard is especially powerful, as you can completely dominate an enemy for a couple turns, which can alter a battle pretty significantly.

[Easy_Lee]

Takes two players, but perhaps you'll like this combo:

Open Hand Monk
Diviner Wizard
Level 17

Greater portent allows the wizard to roll 3d20. One of those is likely to be below 10. Open Hand Monk can deliver up to four Stunning Strike attempts in a single round via flurry, for a cost of 5 ki. Those stunning strikes are used to force a powerful creature to either give up its Legendary Resistance, or be stunned for a round.

Once Legendary Resistance is gone, the monk uses Quivering Palm and activates it next turn. The wizard uses portent to force a low roll. The target dies.

Mind you, I realize most games don't go this high, but the combo is sufficiently broken for me to mention it. It works on anything which isn't immune to being stunned.

[JakOfAllTirades]

Besides spells like Bane and Contagion, and several conditions like Stunned, Paralyzed, etc., are there any other methods for negatively effecting enemies' saving throws?

The Bestow Curse spell is my go-to option for throwing off enemy Saving Throws. At 5th level, no Concentration required. At 9th level, it's permanent until dispelled!