If 'During battle' is stated in your Digimon's Appearance Requirements, they will be made to appear during the Battle Phase, during the timing where special abilities are activated, with the player second to attack going first
Today we'll be looking at the Top Ten plus three Honorable Mentions
(Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.) When a Dragon you control enters, return this enchantment to its owner's hand
It really ruins their days by turning off Delerium strategies, snipes Omnisciences and Occuluses, and has the added bonus of giving yourself a guaranteed land drop every turn in the process, because a lot of times these strategies are dropping lands in their yard like nobody's business
You could also consider including Purphoros, God of the Forge in your deck to make it so that whenever another creature enters the battlefield under your control you can deal two damage to each opponent
On top of that, it has the ability to smash an opponent with 10 damage, albeit the set up may take a while