I like the idea of a battle with a timed outcome, but the mechanic to determine who protects the card makes this weirder than necessary. It would make sense for you to protect the battle yourself since you can get the effect without attacking the battle.

The big issue is that other players can steal the effect which makes this super swingy and also disincentivizes putting the card into your deck to begin with.

Battles where either player can get the effect feels like something from a neutral deck - Planechase-style.

Perhaps there is a better wording for the intent of this card, but this card cycle was meant to replicate the group-hug like incentives that curse of opulence provides. Essentially it's a risk reward for the person deck building as they aren't guaranteed the transformed card (The only upside to having opponents get this effect is that they are attacking another opponent). The effect wasn't meant to be timed but reoccurring, so when the battle is defeated it'll return after the time counters are removed and a new defender is selected. Each color has a minor etb that can be beneficial, and a powerful effect (for not needing to pay mana) on the transformed half. To provide an incentive to defending battles, I plan on designing cards that reward defense similar to monarch but I've haven't put much thought into it yet. I just wanted to expand the battle card type and see what can be done within its limitations. I'm curious how well flipping the mechanic on its head would work such as a battle that the caster defends that has a strong effect for its cost with the downside of it being vulnerable to destruction. The question I keep encountering is whether or not the lack of battle removal will make this expansion of battles too powerful as the only way to destroy them is to damage them which on some board states is a win more card (To some extent damaging any target is the most reasonable removal). Curious on your thoughts overall, I think this new card type has a lot of possibilities to be explored!