When you equip chillshard on a champ with adept arcanist and attack psychic it will get catalyst frost. After that champ attack and the enemy champ take the frost DoT, the arcanist champ will get Attack Frost but won't get catalyst psychic. If the same champ had both attacks before equiping chillshard it will get both catalysts. The wording on chillshard doesn't suggest that it gives catalyst only the turn it is equipped.
