Gladiators can be found in gladius cases and are account-bound. What does that mean? They can't be sold, transferred, or delegated, and if someone leaves a guild for another, their gladiators follow.
Gladiators can only be used in brawls, not in ranked battles.
There are discussions of creating gladiators-only tournaments, which would be an external use case to brawls. Or to be able to use them in challenges.
Only 1 gladiator per battle can be used. All gladiators have the Bloodlust ability.
Gladiators are subject to both fray-specific max limit, but also based on the level of the Barracks (Unleash tactics level).
Gladiators count for collection power and they can be burned for DEC.
Besides the Guild Store level 2+ requirement to be able to purchase gladius cases, to use gladiators in combat, the guild's Barracks needs to be level 2+.