So, Ciel has just arrived on the JP server and she has quite the interesting kit - specifically, her 3rd skill. If you're not aware, that skill disables command cards for your other two servants (1 time, 1 turn) and shuffles the deck, basically forcing all 5 of Ciel's command cards to appear instantaneously.
When you also factor in the environment, that is, using Koyanskaya, Oberon etc to generate starts immediately, here are just a few of the possible applications - keep in mind that her NP is ST:
Clearing a 1-enemy wave entirely through command cards, generating upwards of 70% charge in the process
Clearing a 2-enemy wave with NP and command cards (NP-Q-A-EX chain), also generating upwards of 70% charge in the process
Clearing a 3-enemy wave with NP and command cards (B-NP-B-EX, for example)
BBB infused with crits for the final wave
Also. her 3rd skill is on a 6T cooldown, so it's very easy to use it twice within 3 turns with Koyanskaya and the 5th append. This leads me to conclude that the 4th and 5th appends, and also the Class Score system, are more impactful for Ciel than for most servants and that she has crazy potential. If only she wasn't so close to Space Eresh...