by activation of abilities, does it mean only clickable actives?
Yes. It's like "when a spell is played", except for abilities instead of spells.
For example:
When Deflagration is played vs. when "shatter" is activated.
When Earthquake is played vs. when "tsunami" is activated.
When Rage Potion is played vs. when "berserk" is activated.
List of abilities Invader concerns (incomplete list)
Scavenger
Dead and Alive
Dive
Note: Invader does not mimic "scavenger".
Full list of abilities that are subject to the quanta drain and the Invader's reactionary effects:
* Ablaze - Invader gains +2/+0
* Adrenaline - None.
* Aflatoxin - None.
* Antimatter - None.
* Black Hole - Enemy loses 3 quanta in each element and you gain 1 HP for each quantum lost.
* Burrow - Invader's ATK stat is halved and Invader becomes burrowed.
* Congeal - None.
* Dead and Alive - A death effect is generated.
* Deja Vu - A copy of Invader is generated on your side of the field. Invader does not become lobotomized.
* Destroy - None.
* Devour - Invader gains +0/+1
* Dive - Invader's attack is doubled until the end of your coming turn.
* Endow - Invader's current ability (vampire) is replaced with the targeted weapon's ability and Invader gains +0/+2.
* Evolve - Invader turns into a Shrieker and loses the "invader" passive.
* Gravity Pull - Invader gains the status "gravity pull" (and your other creatures lose this status).
* Growth - Invader gains +2/+2.
* Guard - Invader becomes delayed until the end of your coming turn.
* Hatch - Invader turns into a random creature and loses the "invader" passive.
* Heal - None.
* Improved Mutation - None.
* Infect - Invader dies.
* Infection / Inflate - None.
* Liquid Shadow - None.
* Lobotomize / Psionic Wave - None.
* Luciferin - You heal 10 HP and all your vanilla creatures gain the ability "bioluminescence".
* Lycanthropy - Invader gains +5/+5.
* Mitosis - An (out-of-card) Invader is generated on your side of the field.
* Mutation - None.
* Nymph's Tears - None.
* Paradox - None.
* Petrify - None.
* Photosynthesis - You gain
per activation.
* Plague - Invader dies. All enemy creatures gain 1 infection counter.
* Poison - Enemy gains 1 poison counter.
* Precognition - Reveal enemy hand and draw 1 card from your deck.
* Rage - None.
* Reverse Time - None.
* Scarab - A scarab is generated on your side of the field.
* Sniper - None.
* Steal - None.
* Steam - Invader gains +5/+0. It does not lose ATK when it attacks.
* Stone Form - Invader gains +0/+20.
* Tsunami - None.
* Web - None.