Karlach, Tiefling Spellrager would fit well in an aggressive Izzet (blue-red) deck that focuses on quick damage and spell synergy, utilizing its first strike and haste to pressure opponents early

3 Blightwing Bandit Bloodthirsty Conqueror Bone Picker Bonepicker Skirge Cairn Wanderer Crystalline Giant Death-Hood Cobra Deathgaze Cockatrice Dragonlord Silumgar Dreaded Bat-Cloud Dreadwing Scavenger Feral Deathgorger Fleetfeather Cockatrice Fumulus, the Infestation Green Goblin, Revenant Grendel, Spawn of Knull Hornet Queen Indominus Rex, Alpha Kathril, Aspect Warper Kessig Recluse Kura, the Boundless Sky Malakir Familiar Neriv, Crackling Vanguard Nightveil Predator Nu and Sumi, Career Criminals Odric, Blood-Cursed Odric, Lunarch Marshal Old-Fashioned Vampire Poison-Tip Archer Qarsi Revenant Rayami, First of the Fallen Rodolf Duskbringer Scriv, the Obligator Searchlight Geist Seraph of the Scales Soulflayer Tegwyll, Duke of Splendor Teysa, Opulent Oligarch The Swarmweaver Thornweald Archer Thunderous Orator Tidehollow Strix Topaz Dragon Urborg Scavengers Vampire Nighthawk Vengeful Reaper Venomthrope Verrak, Warped Sengir Wispdrinker Vampire Witherbloom, the Balancer Zagras, Thief of Heartbeats

Let's look at some underplayed cards for her
US UK Where to buy Disney Lorcana: The First Chapter Gift Set The Disney Lorcana Gift Set includes four booster packs, two collectible oversized foil cards and two playable foil game cards
The precons have always been quite good decks
Since the only real version of Nexus of Fate that existed was foil, and foils curl so much, it was actually illegal to play the real copies of Nexus of Fate in some competitive events since the curling made it possible to cut your deck to the copies of Nexus