3-6 MERCURY
3-6 Mercury is the 6th stage of Cosmos Ch.3 — Even Stars Burn Out. Previous stage: 3-5 Venus. Next stage: 3-7 Sun.
Kid Tappa carries a Barrier (up to 15,000 HP) — your hits are absorbed until it's broken.
LI'L GROSS CAT B 30% Barrier Breaker. Also fits “Counter Alien.” 
SPACE CAT A 50% Barrier Breaker. 
FENCER CAT A Guaranteed 100% Barrier Breaker at long range — the reliable accessible breaker. 
BORA S 100% Barrier Breaker reliably cracks Star Alien Barriers. Also fits “Counter Alien.” 
LUMINA S 100% Barrier Breaker opens Star Alien Barriers for the team. Also fits “Counter Alien.” 
SKIRT CAT B 30% Barrier Breaker. Kid Tappa, Shibalien Elite, Scissoroo and Star Peng are Alien. Anti-Alien units take less damage and deal more.
GROSS CAT A Its True Form is Strong Against Alien, giving budget anti-Alien value. LI'L GROSS CAT B True Form has a 30% Knockback vs Alien. Also fits “Break the Barrier.” 
WHEEL CAT A Deals Massive Damage to Alien enemies — a huge area nuke against Alien crowds and bosses. Also fits “Clear the crowd.” 
LITTLE LEAGUER CAT S Resistant vs Alien and Long Distance — a budget anti-Alien backliner. Also fits “Break the Barrier.” 
CATMAN S Deals Massive Damage to Alien in every form. Also fits “Clear the crowd.” 6 enemy types stack up here. Area attackers hit the whole push at once instead of one unit at a time.
VALKYRIE CAT A Hits the whole group while it freezes them. WHEEL CAT A Hits every Alien in a wide area at once, melting grouped Star Aliens. Also fits “Counter Alien.” 
SURFER CAT A Area damage hits grouped enemies. Also fits “Counter Alien.” CATMAN S Long-range Area damage clears groups. Also fits “Counter Alien.” 
ACTRESS CAT B Hits multiple enemies at once for budget crowd damage. Kid Tappa: 40k HP + 15k Barrier, low damage. Can be used as a stepping stone for Crimson Mina / Polevaulter / Jellycat once the Barrier breaks.
Kid Tappa replaces UltraBaaBaa as the front-line miniboss; Scissoroo adds 2,800-AP Knockback pressure; Star Peng still anchors the backline. r/battlecats's read: 'Mercury Ch.3 punishes lineups that lean on Crit Cats — Kid Tappa is a wall, not a Metal.' Mag scaling means even peons hit for 5k+; your meatshield rotation matters more than your DPS pick. Lineup: Manic Mohawk + Crazed Lion + Cyborg Cat (Knockback-Immune) → Warp-Immune Anti-Alien Ubers (Lumina, Bora/Pixies, Mighty Reza) → A. Bahamut for Kid Tappa burst once Barrier breaks. Common failure: stacking too many slow-rate Ubers under MAX 20. You need volume of attacks to outpace Star Peng warp + Scissoroo knockback — slow Ubers spend the stage swinging at empty air.
The castle you destroy to clear the stage.