The Spirit Guardians spell changes a creature's speed while they're in the area:
An affected creature's speed is halved in the area
The Ray of Frost spell temporarily changes a creature's speed on a hit:
On a hit, it takes 1d8 cold damage, and its speed is reduced by 10 feet until the start of your next turn.
If my human cleric is concentrating on Spirit Guardians while adjacent to a gladiator (speed 30 ft.), and my ally the sorcerer hits the gladiator with a Ray of Frost, how many feet can the gladiator move (without dashing) on his next turn?
Does the half-speed effect from Spirit Guardians apply before the 10-foot reduction from Ray of Frost, thus making the gladiator's speed
(30 ÷ 2) - 10 = 5?Does the 10-foot reduction from Ray of Frost apply before the half-speed effect from Spirit Guardians, thus making the gladiator's speed
(30 - 10) ÷ 2 = 10?Do they interact in some other way?