You can use it immediately as a removal spell, and many times, the activated ability will be relevant, especially against Commander staples like Swiftfoot Boots
It also triggers the abilities of cards that look at targeting effects, like Cowardice, which could spell the end for any strategies you may have with your mutations
After activating Sinkhole your opponent will most likely need to recover and play sites
Modular creatures, such as Arcbound RavagerArcbound Ravager, Arcbound CrusherArcbound Crusher, and Arcbound ReclaimerArcbound Reclaimer, also get a massive benefit from the counters
As we talked about earlier, Krark-Clan Shaman is an insane way to beat red decks, but it's also very good at a bunch of other decks when you Toxin Analysis it, especially since Refurbished Familiar flies and can swing over the leftovers