The effect of the “Gladiator Beast” monsters that says, “At the end of the Battle Phase, if this card attacked or was attacked, you can return it to the Deck…”, returning the “Gladiator Beast” monster to the Deck is a cost to activate the effect.
If you do not have any “Gladiator Beast” monsters remaining in your Deck that you can Special Summon, you cannot activate the effect of the “Gladiator Beast” monster that attacked or was attacked. For example, if “Gladiator Beast Murmillo” attacks or is attacked and the only “Gladiator Beast” monster remaining in your Deck is another copy of “Gladiator Beast Murmillo”, you could not activate the effect of “Gladiator Beast Murmillo” at the end of the Battle Phase.
If a “Gladiator Beast” monster attacks or is attacked during the Battle Phase and the “Gladiator Beast” monster becomes flipped face-down by an effect during the Battle Phase, even if the “Gladiator Beast” monster is flipped face-up before the end of the Battle Phase its effect to Special Summon another “Gladiator Beast” monster cannot be activated.
“Divine Wrath” can be chained to the effect that returns the “Gladiator Beast” to the Deck. The effect will be negated, but the “Gladiator Beast” monster will not be destroyed because it is in the Deck.
If 2 or more “Gladiator Beast” monsters attack or are attacked during the Battle Phase, at the end of the Battle Phase the effect of each “Gladiator Beast” monster can be activated. The effects will activate and resolve separately. They are not combined onto the same Chain.
If a “Gladiator Beast Alexander” is Special Summoned and later it is removed from play using “Interdimensional Matter Transporter”, when it is returned to the field its “unaffected by the effects of Spell Cards” effect will still be applied.
If a “Gladiator Beast Alexander” is Special Summoned and later it is flipped face-down by another card’s effect, when it is flipped face-up the “unaffected by the effects of Spell Cards” effect will not be applied.