the line for whats bad in Magic is subjective, especially in Commander
Non basic lands are the first cards where I actually care about the ability box
The Epic Ingredients TiamatTiamat is a setup commander, and as such, building a deck around it means that we need to answer one simple question: how are we going to use the cards she tutors up
Since amass doesnt target, removing the Army in response doesnt cause that spell to fizzle

Abstruse Interference Adverse Conditions Afterlife Insurance Ancestors' Aid Angelic Favor Ashling's Command Assimilate Essence Auspicious Arrival Bake into a Pie Banish into Fable Battle Menu Beckon Apparition Blast from the Past Blessed Defiance Blooming Blast Brackish Blunder Broken Visage Cackling Counterpart Charge of the Mites Commence the Endgame Corpse Cobble Crumb and Get It Crush Dissent Cunning Maneuver Dance with Devils Deadly Derision Deadly Dispute Deceive the Messenger Depths of Desire Desculpting Blast Drag the Canal Eldrazi Confluence Elminster's Simulacrum Errand of Duty Espers to Magicite Excise the Imperfect Exotic Pets Eyes in the Skies Fake Your Own Death Fanatical Offering Fated Infatuation Fateful Absence Feast or Famine Feed the Cauldron Felonious Rage Flip the Switch Fractal Anomaly Fungal Infection Geist Snatch Glen Elendra's Answer Glimmerburst Gnawing Crescendo Grave Birthing Great Train Heist Grip of Phyresis Hire a Crew Hornswoggle Humble the Brute Inkshield Into the Flood Maw Intrude on the Mind Jace's Scrutiny Kaya's Guile Launch Mishap Lazotep Plating Lithobraking Lorehold Command Lost Days Magma Opus Make Your Mark Merciless Repurposing

When you cast it, you get to gain control of a creature in play and then turn it into a 10/10, give it trample, annihilator 2 and haste until the end of the turn