by Planetary
The cards:Arachnarok Spider: Battlefield only. Feared 1. Action: When you play this unit from your hand, put up to 2 Goblin units into play in your battlefield from your hand.
Mork's Teef Ritual: Action: Sacrifice an Orc unit to put a unit into play from your hand. Then, deal 3 damage to a section of your capital.
From the FAQ:
Play
“Play” means to play from the hand,
paying all costs and following all
restrictions.
Put into Play
“Put into play” means that the card
enters play through a card effect
instead of through normal costs and
restrictions. An important distinction is
that put into play does not bypass the
unique restriction or any restrictions in
the text box of the card.
If you put the Spider into play with the Ritual, you are not playing it from your hand. Its effect depends upon it being played from the hand, so it cannot be triggered. "Put into play from your hand" is NOT a subset of "play from your hand". The latter requires you to pay the card's cost, the former doesn't.