Yhyjyk

Backstory: I’m currently working on a level 20 character build for a one shot I’m doing, I want to play a level 15 Beast Master Ranger/ level 5 Divine Soul Sorcerer. By doing such I’m giving Myself access to a slew of good spells that interact with the Share Spells feature.

Scenario: (Allowing the Multiclass, and assuming all stats are in place without issue for any following abilities) If I cast haste on myself within 30 ft of my Companion, the spell should essentially duplicate onto my companion. By doing so I want to make sure I understand how combat would ensue within said combination.

Question Round of Combat:

• First Scenario (Haste doesn’t state that I can explicitly use my voice to shout a command, but it also only lets you do actions you can Normally do, so I’d like clarification here)
  1st Turn: Cast Haste.
  2nd Turn: Take the Attack action and trigger bestial fury, (2 attacks for my companion and 1 for me), Take second Attack action and give up my attack for an additional Bestial Fury (2 more attacks from my companion), uses bonus action accordingly.




• Second Scenario
  1st Turn: Cast Haste.
  2nd Turn: Take Attack action and trigger Bestial Fury, (3 attacks Beast has 2 actions and splits attacks as such with bestial fury Multiattack and then singular attack from haste action for my companion one for me), haste action attack for me, uses bonus action accordingly.




• Third Scenario:
  1st Turn: Cast Haste.
  2nd Turn: Take attack action and trigger bestial fury, (2 attacks for my companion one for me), Take Haste Attack action (Companion doesn’t get additional action as each action requires a command and I can’t command it with my extra action), take bonus action accordingly.

The third scenario seems like the most likely out of all of the situations but I wanted to make sure I wasn’t missing anything or there hadn’t been any Sage Advice or oversight on my part.

RAW, I think you're in Scenario Three.

Beast Master companions are a little weird -- they don't take their turns themselves, but must be ordered to take an action by their master, so having a hasted companion isn't going to increase their number of attacks without also increasing the number of commands given. (And even then, they need to be able to have the action available to do that)

Haste explicitly states the actions its additional action allows:

...Attack (one weapon attack only), Dash, Disengage, Hide, Use an Object

Because "Verbally command your beast..." isn't one of them, it can't be used as a haste additional action.

Likewise, Bestial Fury substitutes your beast attacking twice / multiattacking for your entire attack action.

So Scenario One fails because you can't use the haste action to command your beast.

Scenario Two fails because even though a hasted Companion has a haste action, it can't use it (Though I could see an argument that an Action Surge could accomplish this) without being ordered.

Scenario three, where you get one extra haste action attack, and your companion has but can't use its haste action, is where the standard rules end up.