Optimizing Animate Objects spell against nonmagical damage immunities

Question

Suppose I am a Wizard who likes to cast Animate Objects in combat. At my present level, I am likely to encounter foes with resistance or immunity to nonmagical physical damage. As detailed in this answer, my fifth-level spell is indirectly subject to the same taxation as that imposed upon mundane weapon attacks.

Suppose I am a very stubborn Wizard who insists on casting Animate Objects regardless of creature matchup. What methods can I employ to make the spell effective against creatures with nonmagical BPS resistance?

Ideal answers involve using the spell to deal damage. However, I am open to non-damage alternatives if they provide a reasonable combat advantage.

Answer 1

Use silvered weapons as objects

Some of the creatures that have resistance to nonmagical slashing, bludgeoning and piercing can be normally wounded with weapons that are silvered. This does not work against all of them, but it for example works against many devils. It also works against were-creatures.

Depending on your DM, they may require a more expensive alchemical silvering procedure, or they might just be OK with plain silver objects (although technically, those are not silvered weapons).¹

Also, to maximize damage output, use the version that uses 10 tiny objects. That will give you in general a higher damage output overall per turn, than using fewer but larger objects.

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¹ If you want to get very technical about it -- in the way a computer program running the spell might -- there is the question if the attack of a a silvered dagger that you animate as a tiny object count as a silvered attack. The consensus is that anything silvered wether weapon, improvised weapon or armor would overcome the resistance, so it would be weird if silvered creatures could not.

Thankfully, you have a DM that is not a computer program, to adjudicate that. The spell already provides precedence for the DM changing the type of damage based on the type of object:

It makes a slam attack with an attack bonus and bludgeoning damage determined by its size. The GM might rule that a specific object inflicts slashing or piercing damage based on its form.

In practice I'd be very surprised to see a DM rule that an animated silvered dagger does not count as a silvered attack (and a piercing one, at that).

If you have such a DM, it is not entirely clear to me if you can give silvered weapons (maybe made to order) to tiny or small animated creatures with hands to wield them, because these objects are pretty dumb. They have only Intelligence 3, which is comparable to a dog or cat, while apes like chimps or ogres, who are dumb but able to use tools, have at least Intelligence 5. The ogre zombie is as dumb but can use the club it used in life, though, so maybe you can convince the DM. In that case, as @DavidCoffron points out, an even better strategy is to give magic weapons to your objects, if you happen to have them -- this works against all creatures with resistance to non-magical damage.

Otherwise, you are down to just using tiny objects to maximize your damage. This is among the single target sustainable damage spells with the highest damage at its level, so even with resistance, 10 tiny objects it is not that bad.

Answer 2

Give small animated objects magic weapons

If your animated objects have hands, you could provide them with magical weapons. There are even common magic items that could be crafted or purchased relatively cheaply such as the moontouched sword from Xanathar's Guide to Everything:

Weapon (any sword), common

In darkness, the unsheathed blade of this sword sheds moonlight, creating bright light in a 15-foot radius and dim light for an additional 15 feet.

The objects would lack proficiency (dropping the chance to hit by 20%), but your damage output would still be greater since you could get past resistance (and certainly better against immunity). Below are the damage per round outputs assuming a level-appropriate 18 AC with resistance (using a rapier for Dexterity-base sizes, and a greatsword for Strength-based sizes):

Size	Slam Attack (resisted)	Moontouched Sword
10 Tiny	17.875	*
10 Small	14.625	16.25
5 Medium	8	5.5
2 Large	5.85	4.5
1 Huge	4.675	3.85

As you can see, the 10 tiny creatures are dealing more through resistance than the small creatures can with the magic weapons. To get past this limitation you would need a +1 weapon which is quite a bit more expensive or harder to collect, but gets you the following chart:

Size	Slam Attack (resisted)	+1 Weapon
10 Tiny	17.875	*
10 Small	14.625	22.5
5 Medium	8	8.125
2 Large	5.85	6
1 Huge	4.675	4.8

This would be boosted even further with more powerful magic weapons, but remember that animate objects doesn't last long enough to get attunement.

Tiny creatures and weapon sizes

You'll notice that I excluded the tiny creatures from the charts above. This is because tiny creatures can't wield normal weapons without disadvantage. The Dungeon Master's Guide states:

A creature has disadvantage on attack rolls with a weapon that is sized for a larger attacker. You can rule that a weapon sized for an attacker two or more sizes larger is too big for the creature to use at all.

...so a tiny creature only deals (disadvantage on the weapon attacks):

Size	Slam Attack (resisted)	Moontouched Sword	+1 Weapon
10 Tiny	17.875	10.413	15.2

If we were to get properly-sized tiny magic weapons, it isn't clear whether they deal full damage. For example, the sprite's weapons get their weapons changed to 1 damage:

Longsword. Melee Weapon Attack: +2 to hit, reach 5 ft., one target. Hit: 1 slashing damage.

Shortbow. Ranged Weapon Attack: +6 to hit, range 40/160 ft., one target. Hit: 1 piercing damage...

If we use reduced-to-1 weapons, we get the following table:

Size	Slam Attack (resisted)	Moontouched Sword	+1 Weapon
10 Tiny	17.875	17.05	24

...so if you can find or craft 10 tiny-sized +1 weapons than this would be worth it, but it is probably much easier to get 10 medium-sized +1 weapons and give them to the small creatures (at the cost of only 1.5 DPR).

If your DM allows the tiny creatures to still do full damage with their weapons (as seen in with the quickling's weapons), you get the following table:

Size	Slam Attack (resisted)	Moontouched Sword	+1 Weapon
10 Tiny	17.875	29.75	38

...making the investment in tiny-sized magic items much more worth it.