Like most Pokmon cards, the value of Articuno depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Legendary Collection)
The main line of play is simple but powerful: develop ink early with Sapphire, then drop mid-to-late-game glimmers that generate Lore more efficiently
Thats not even considering the more straightforward A+B infinites you can sneak into this theme, like Grand Architect with Pili-Pala, Painters Servant with Grindstone, or Rings of Brighthearth with Basalt Monolith
Well keep on adding to this list as further details are revealed for Japanese sets, and you can be sure that well also add card lists for each set as and when card images are shown too
Even evoke if you were out of lands or had no other play
More concretely, it doesn't help that Delta Reign comes immediately after Pitch Black, and that Mega Rayquaza ex's SIR looks in some ways very similar to Mega Darkrai ex's