If an opponent's commander would die, that player may choose to save it and move it to the command zone before Ravenous Slime gets a taste of it, or that player may choose for Ravenous Slime to exile their commander and then save their commander from exile and move it to the command zone
If you untap mana rocks, this could be mana neutral
Any colours that are adjacent to each other - such as Black with Red or Blue, or Green with White or Red - are allied colours
Spells and creatures look better with art that has strong foreground subjects
So, while Flare of Denial is a free counterspell, you need to sac a blue creature
Sylvan Reclamation Sylvan Reclamation works best at slower, lower-powered tables where you have time to utilize slow fixing or an equally slow 2-for-1