If a creature has more than one instance of riot for whatever reason, you can choose a different option for each instance
So, Celebi ex would only need one energy card to attack, and with just two energy cards, it could potentially deal with 200 damage
The ability to both draw a card when your stuff is targeted (and before resolution, so you can draw a card to respond to it) and to keep your foes from drawing more than one is very powerful for a 4/4 3-drop that gives you ramp, removal, and countering
City in a Bottle will wipe out any permanent from the Arabian Nights expansion, and it won't let players play any more cards from that set, either
20 | Copy each card exiled with Wizard's Spellbook
It also aligns them with other spells of the same mana value