All that is required to activate an effect card is to play it in an appropriate action. What form an appropriate action takes will depend on the nature of the card. Magic spells need to be cast; hand grenades must be thrown; force fields have to be switched on.
Players can use other cards with the effect card in the activation action if they are appropriate, such as using the Throw skill card with the hand grenade or using Spell Casting expertise with the magic spell.
Once the activation is successful the card's second set of keywords immediately takes effect.
All activation actions have to overcome a resistance. Often, especially for beneficial effects, this resistance will be the basic score of one, almost guaranteeing success. However disadvantageous effects aimed at another creature will be resisted by the target, who may use whatever cards are appropriate in their defense.
Situation bonuses including range and cover will also increase the resistance. Indirect attacks and cards with the Area Resistance keyword will add to the resistance depending on the number of squares targeted. Any creatures in the square or squares targeted by the activation action also add to the resistance, with each creature adding their minimum resistance of one even if they do not want to add to the resistance.
There are two possible outcomes when an activation action fails to beat the resistance.
The most common is that the activation simply fails. The spell fizzles out or the plasma field refuses to energise. The cards played in the action return to the deck or otherwise behave according to their individual keywords.
Some activations are combined with an attack, particularly indirect attacks such as a hand grenade. In these circumstances it is assumed that the activation was successful but the attack aspect missed its target. The effect card is active and follows its effect keywords, but the effect is not where the player intended it to be. The Game Leader should randomly determine where the effect is located.