How can solo Crusher Swarmkeeper best leverage forced movement?

Question

The Swarmkeeper¹ Ranger’s Gathering Swarm¹ feature applies one of three effects to one attack each round, one of which is forcing the target of the attack to move 15 feet if they fail a Strength save. The Crusher feat allows you to move the target of your bludgeoning-damage attack 5 feet, no save, also once per turn. Using magic stone,² I can make Wisdom-based ranged attacks that deal bludgeoning damage, allowing me to maximize both my accuracy and my save DC. So I can push people around.

What or where am I pushing them? There may be environmental hazards I can leverage, or with a party, perhaps my party can create some. But what about solo, when the environment isn’t inherently hazardous? Ultimately I’m talking about one cantrip, one feat, and three class levels to achieve these features—there’s a lot of room there to potentially add synergy. Is there some synergy I can build into the same character which rewards my ability shove people around? The big concern I have here is actions—if I multiclass to access spells that create hazardous zones, that usually means an action to produce them, and then I can get to shoving.

Good answers will (probably) point options in one or more of these flavors:

• Ways to generate hazardous zones that are especially action-efficient. Things you can create as a bonus action (or no action?), or things that are permanent (or long-duration) and portable, perhaps. For example, if forced movement provoked attacks of opportunity (it doesn’t), then a companion that can take opportunity attacks would be a great solution, since I could push enemies past the companion and trigger those attacks.

  That approach might still be viable for this, if I can force their movement away from me and then they have to move on their own turn back towards me and trigger opportunity attacks. But it seems in that case that most are probably just going to eliminate my companion. Maybe there’s a situation, though, where the “companion” is not really attack-able—a spell effect, perhaps.

• Ways to turn very-common environmental features into hazards. For example, D&D 3.5e had a Dungeoncrasher³ Fighter, which could deal very high damage by shoving people into walls. Walls are common enough environmental features to feel comfortable relying on them.

• Ways to directly punish movement—effects that deal more damage the more you move, perhaps. Again, obviously, strong preference for those that are compatible with forced movement, though if I force them away and then they have to walk to me maybe that’s enough.

Any Wizards of the Coast-published material is acceptable, with the exception of Unearthed Arcana material that has since been superseded by later Unearthed Arcana material or official publication. Please note the sources of any material used. I am specifically seeking D&D 5e expertise here—I want to see judgment and analysis of how effective a proposal is, what its potential pros and cons are. One big part of this is going to be comparing the build against other builds that can do similar things—for example, if suggesting a build that relies on opportunity attacks being provoked as the target moves back towards me, that should be compared against other builds that use, for example, dissonant whispers so that the target provokes coming and going. Likewise, do Swarmkeeper,¹ Crusher,¹ and magic stone² even make sense when I could just go with eldritch blast and Repelling Blast⁴ and/or Grasp of Hadar²?

1. _{Tasha’s Cauldron of Everything}
2. _{Xanathar’s Guide to Everything}
3. _{Dungeonscape, a 3.5e supplement}
4. _{Player’s Handbook}

Answer 1

It sounds like you're looking for the spike growth spell. This is a second-level ranger spell (available at level five) which says:

The ground in a 20-foot radius centered on a point within range twists and sprouts hard spikes and thorns. The area becomes difficult terrain for the duration. When a creature moves into or within the area, it takes 2d4 piercing damage for every 5 feet it travels.

This lets you convert your 20ft of push into 8d4 damage (average 20).

You could stand near the center of this damage zone. In theory, against a single opponent, you could get into a situation where you push them back 20ft (see: pushing ignores difficult terrain) and then they have to spend 40ft of movement to get back into melee range, and both directions inflict 2d4 damage per 5ft of movement.

In terms of damage, you'd be looking at 1d6 (magic stone) +4 (WIS) + 8d4 (spikes) = 27.5 average damage. Or 47.5 average damage, if the monster ran back at you across the spikes!

For comparison, a fifth-level ranger might do 2*(1d8 (longbow) + 4 (DEX)) + 1d8 (Colossus Slayer) + 1d6 (Hunter's Mark) = 25 average damage, at a higher attack bonus due to archery stance.

Optional ways to improve this include:

• multiclass to sorcerer to get quicken spell so you can deploy your spike growth more quickly
• invite your spellcaster friends to use moonbeam and spirit guardians and wall of fire so you have more damage zones to punt creatures into

Of course this doesn't work if you miss, or if they make their save. It works poorly if you have disadvantage because they're standing next to you. It doesn't work at all against ranged attackers or fliers, and it scales poorly if you're attacked by more than one opponent.

Overall this approach seems bad, simply because there are so many situations where it doesn't work, and then you've invested a lot of resources into a trick that you can't use.

(Also, it's often a bad idea to create a character with a trick that trivializes encounters, because many DMs will react by generating encounters where you can't use your trick.)

However I do think there's the potential for a good build that went Swarmkeeper Ranger, did not go for high WIS or Magic Stone, but did keep a spike growth effect on the battlefield for use whenever the swarm ability activates. This comes at a cost because it replaces your concentration for hunter's mark but seems likely to be worth it.