The CGC slabs have ridges and they stack, but they don't stay together securely
Buyback [cost] means You may pay an additional [cost] as you cast this spell and If the buyback cost was paid, put this spell into its owners hand instead of into that players graveyard as it resolves. Paying a spells buyback cost follows the rules for paying additional costs in rules 601.2b and 601.2eg
You copy that spell once plus an additional time for each opponent who copied the spell this way
Dark Depths Okay, I will admit that this one just brings me way too much joy to not include in this list
Loxi: One of the now famous "do thing, but more!" cards, it's solid
Flamehold Grappler Flamehold Grappler was designed in a set with the flurry mechanic, so you already have a good incentive to cast two spells a turn if youre playing those flurry cards