You can remove 2 A-Counters from anywhere on the field to Special Summon this card from your hand. Once per turn, you can place 1 A-Counter on each face-up monster your opponent controls. (If a monster with an A-Counter battles an "Alien" monster, it loses 300 ATK and DEF for each A-Counter during damage calculation only.) You can only control 1 face-up "Alien Overlord".
Can be Special Summoned by removing 2 A-Counters anywhere on the Field.
Can place 1 A-Counter on all opponent’s face-up monsters, every one of your Main Phase.
If you do not have A-counters anywhere on the Field, you need 1 monster to Tribute Summon.
You can allow your Alien Warrior to be destroyed by battle, in which Alien Warrior will place 2 A-counters on the monster that destroyed it, allowing sufficient A-counters for you to Special Summon Alien Overlord next turn.
This monster cannot be Special Summoned from your Deck to the Field by using Mysterious Triangle.
Due to Alien Overlord’s ability to place A-counters on opponent’s monsters, you can utilize Brainwashing Beam as a follow up to take control of that opponent’s monster, or you can also use Mysterious Triangle to destroy that monster directly, and Special Summon another 1 of your own Alien Monster which is level 4 or lower. “A” Cell Recombination Device can be banished from your Graveyard to search for Alien Overlord from your Deck to your Hand. You can use “A” Cell Recombination Device to send Alien Overlord from your Deck to your Graveyard and place a huge amount of A-counter on either your opponent’s monster or your own monster.
Restart Can be used only once after starting hands are dealt. Reveal and redraw your starting hand.
While one Alien Overlord is on the field, it's actually possible to Set another one, but when the set Overlord is flipped over (such as attacked by opponent), it is instantly sent to the graveyard (then flipped one).
There's tactical use in this. For example with Brainwashing Beam you've controlled an opponent creature, but you want to destroy it, so you can just tribute it to summon the second Overlord.