teach ur cyndaquil smokescreen then when the legendary is in front of u use smoke screan
and all of their attacks will miss then just widdle away its hp if it recovers from
smokescreen just use it again

You use smokescreen when Articuno is near then you use Fire-Type moves.

use only fire type moves

i used all pokemons but i loosed at moltres but i answered the questions and im
felerigator it is easy you need to be level 19 when you fight articuno use petrifity orb
or stun seed when he is parlalysis (sorry for spell) use smokescreen and gotcha then use
alot of fire moves i used like 3 reviver seeds with articuna aahh and when he comes
close with you use blast seed

try training