Revenge of Carnage (Merciless)

Revenge of Carnage is a special stage that consists of a boss fight against Hannya. It appears on the 11th, 12th, 25th and 26th of every month. When clearing this stage, you have a 100% chance to unlock the true form of Express Cat. This is a No Continues stage.

Battleground

 * 2 Znaches will appear after 3.33 seconds.
 * 4 Ginger Snaches will appear after 6.66 seconds. From this point on, nothing else will spawn until you hit the base.
 * Upon hitting the base, Hannya spawns as a boss with a Zigge, Zir Zeal, Znache, Zroco, and Ginger Snache.
 * From this point, the enemy base will spawn a total of
 * 6 Zigges (33.3 to 50 seconds apart.)
 * 4 Zir Zeals (60 seconds apart.)
 * 8 Ginger Snaches (30 to 40 seconds apart.)
 * Unlimited numbers of Zrocos and Znaches (30 to 40 seconds apart.)
 * The difficulty of the map is warding off Hannya and the Zir Zeals. For the latter, a hard hitting zombie-killer uber like Li'l Valkyrie can make this task trivial: a level 40 Li'l Valkyrie only takes 3 hits to end a Zir Zeal. For the former task, the well-known strategy of double Island Cats and Sushi Cat does a good job of holding off Hannya. In particular, building up a wall of these cats against the Zir Zeal, killing the Zir Zeal, and allowing the future Zombies to burrow under this wall of cats allows you to consider both threats separately.
 * The map is shorter than the original stage Hannya appears, Realm of Carnage. This characteristic exacerbates any mistakes related to the burrowing patterns of Zombies.

Strategy
For now, a functional strategy is to equip a hard-hitting zombie killer, double Islands and sushi, dual Erasers, Welterweight Cat, and Vaulter Cat and pretty much spam double Islands and your zombie killers. Li'l Valkyrie carries this stage with ease. I haven't made a no-Gacha run yet, but the reference below has.