The Soulstrike ability comes from Frostmourne and is a custom ability
When you cast a room card, you need to choose which half youre going cast, even if you have the mana to cast both sides
Moreover, both Horn Attack and Waterfall are normal, damage-dealing attacks with no additional effects ( e.g., some Pokmon have attacks that require the player to discard an energy card)
With this, you could guess what kinds of strategies they would try to use, or you could play a card forcing them to discard the top few cards of their deck if you found something you didn't want them to play
Merry, Esquire of Rohan Merry, Esquire of Rohan could be a pretty good equipment commander
If you are out of cards in your hand, even being able to draw two from playing Commodore Guff from your Command Zone can keep you alive and kicking in a game