Sure, Demonic Tutor could get me an Underworld Breach or it could get me something cool and synergistic
We can also use it as a backup plan for casting Saheeli Rai when we dont draw any red mana
Well, Arena of the Ancients is an artifact with an unusual effect
That means you can use it to avoid any targeted spell, any board wipes that destroy things instead of exiling them or just use it to avoid losing creatures in a big attack
You could be green-based: Creatures (23) 3 Drana, Liberator of Malakir 2 Verdurous Gearhulk 2 Armorcraft Judge 4 Winding Constrictor 4 Rishkar, Peema Renegade 4 Walking Ballista 4 Narnam Renegade Planeswalkers (4) Lands (25) Spells (8) Or you could be black-based, taking advantage of Vampire synergies, which well discuss a little later in the week
while they are both powerful colors, they also dont have too much overlap in what they do