used Wild Crimson..1,2,1..is always S/S
Bronze Whelping..1,2,1..also S/S
Nexus Whelping...1,x,x...P/S...same health as Bronze, slower but hits at 305
Crimson dies..Bronze in
Prison (to counter void)
Nexus in, full health
should only take 1 tail
did with me, your mileage may vary, Nexus ended with 71% health
Doesn't work as written - timing is wrong too. (P/S, P/B, H/S) Four attempts exactly as written and apparently entirely dependent on RNG. Turn 5 doesn't exist, either, as Yu'la gets forced out at the end of Turn 4. Fifth attempt tried to use Liftoff with every pet. Still doesn't work. Only try if you have a good stock of bandages and favor with the RNG gods.
The way I managed to do this is by taking 2 dragons with high power, and both Tail Sweep and Lift-Off. Use Yu'la as given, then with your two other dragons, hit Lift-Off when there's 1 turn remaining on the cooldown for Void Gate, Tail Sweep otherwise. I got it with a P/P Spawn of Onyxia and P/H Wild Jade Hatchling.
Using the breeds above with what i had I could not do it. I had to change to my highest dmg P/? whelps which in my case were Onyixia whelpling P/B and Nexus P/P, when I did this I had no issues at all. Use your highest whelps with tail lash