Spirit Troll movement immunities vs Giant Insects web bolt ability.

The Spirit Troll has the following immunities Condition Immunities Exhaustion, Grappled, Paralyzed, Petrified, Prone, Restrained, Unconscious

Giant Insect Spell on the spider summon states Web Bolt (Spider Only). Ranged Attack Roll: Bonus equals your spell attack modifier, range 60 ft. Hit: 1d10 + 3 plus the spell’s level Bludgeoning damage, and the target’s Speed is reduced to 0 until the start of the insect’s next turn.

The Web bolt doesn't give any kind of condition just that it reduced the movement to zero. 

Now thematically the web bolt is hitting the creature and webbing it to the ground to prevent movement.   Which would be grappled or restrained which the Spirit Troll is immune to right? 

We had a roll off for the rule for that session but I wanted to make sure I get it correct for future sessions. 

Does movement drop to zero for a creature that is effectively immune to movement impairing effects due to the lack of status effect?   What about the Freedom of Movement Spell? 

Thanks in advance. 

RAW, the ability works normally on a spirit troll. Thematically, the ability should probably include a statement that it does not work on creatures immune to the Restrained condition.

Thanks for the feedback. 

Also, you're presumably the DM. Making rulings on the fly when things are unclear or seem to work weirdly is part of your role in the game.

It's completely legit to say "the troll can't be restrained, and that includes the more limited effect of web bolt".

As for Freedom of Movement:

and spells and other magical effects can neither reduce the target’s Speed nor cause the target to have the Paralyzed or Restrainedconditions.

So, by the rules... maybe? Is the web bolt, coming as it does from a summoned creature, a magical effect? Probably not. It certainly wouldn't protect against a normal giant spider's webbing.

Quote from jl8e >>

Also, you're presumably the DM. Making rulings on the fly when things are unclear or seem to work weirdly is part of your role in the game.

It's completely legit to say "the troll can't be restrained, and that includes the more limited effect of web bolt".

 

If we cant find the rule in 2 minutes we have a roll off for that session.   I won the ruling for that session.    Mostly wanted to make sure I made the right call and it looks like I didn't.