Essentially, if it made you choose one or more options, regardless of card type, it made the cut so I could showcase the best flexible spells Magic has for you
High tactical value

The deck: Merfolk Tribal Comparative Analysis 34 Lands 12 Ramp : Hakbal of the Surging Soul, Nicanzil, Current Conductor, Thieving Skydiver, Sol Ring, Stonybrook Banneret, Simic Signet, Patchwork Banner, Thrasios, Triton Hero, Deeproot Wayfinder, Thada Adel, Acquisitor, Twists and Turns (late), Kioras Follower 11 Target Removal : Thada Adel, Acquisitor (kinda), Vodalian Hexcatcher, Chomping Changeling, Lullmage Mentor, Harbinger of the Tides, Disruptor of Currents, Repulsive Mutation, Tishanas Tidebinder (kinda), Empress Galina, Thieving Skydiver (kinda), Champions of the Shoal (kinda) 3 Board Wipes :Wave Goodbye, Aetherize, Summon: Leviathan 2 Graveyard Recursion : Deeproot Historian, Quandrix Command (to library) 1 Graveyard Hate : Scavenger Grounds 4 Tutors : Forerunner of the Heralds, Merrow Harbinger, Seahunter, Twists and Turns (late) 12 Protection : Ripples of Potential, Singer of Swift Rivers, Svyelun of Sea and Sky, Kopala, Warden of Waves, Roaming Throne (self-protection), Inspiring Call, Vodalian Hexcatcher, Lullmage Mentor, Tishanas Tidebinder, Disruptor of Currents, Summon: Leviathan (self-protection), Repulsive Mutation 15 Card Draw : Hakbal of the Surging Soul, Kumena, Tyrant of Orazca, Svyelun of Sea and Sky, Emperor Mihail II (kinda), Seafloor Oracle, Cold-Eyed Selkie, Inspiring Call, Namor, Scourge of the Seas, Benthic Biomancer, Attuma, Atlantean Warlord, Kiora, the Rising Tide (1/2), Thrasios, Triton Hero, Aquitects Will (1/2), Harmonized Trio, Prime Speaker Zegana, Summon: Leviathan 6 Finishers/ Surprise /Alternate win conditions : Herald of Secret Streams, Master of the Pearl Trident, Lord of Atlantis, Mist Dancer, Simic Ascendancy, Namor, Scourge of the Seas As we see from the comparative analysis, the rates per category are very good

Pokemon cards of this type sometimes carry abilities that can attach energy cards from one's deck, hand, or discard pile to an ally with little to no effort, so a Grass deck themed around this should be able to bring out Pheromosa & Buzzwole's true potential.
Devouring Light is probably the best removal spell with convoke (with Conclave Tribunal following closely behind)
#4 - Counter Intelligence Another time, I may tally up themes and how often they appear, but even a cursory glance reveals that Counter Intelligence deck felt like a fresh new package