Previous Versions can be found here.
Mettaton NEO was added during Beta 4.3 as a new Legendary card. After multiple effect changes and discussions, he was finally added to the game with the effect of dealing his attack as damage to all enemies upon dying, but cannot attack himself. However, as of Beta 11.0, it now also deals that damage to ally monsters.
This is particularly effective as a means to clear the entire board of enemy monsters, as well as a deterrent to cards such as Woshua, Strafe and Tsunderplane.
Undertale OST - Power of "NEO" Extended
NEO's Theme when played. It ends at 0:06. The song shown here is how it is in the game, which is slightly slower and lower pitched than how it is in Undercards.
Combos
Best used in Determination, Bravery, Patience, Perseverance and Justice, all with different strategies. Keep in mind that you might want to leave your board as empty as possible before executing these:
- Bravery: Increasing his ATK with Strength. (Snowdrake with other SOULS.)
- Patience: Giving him Taunt with Protection. (Glad Dummy with other SOULS.)
- Determination: Apply Another Chance to it before killing it. It can then use its Dust effect again (but for 6 damage).
- Perseverance & Justice: Using Worsening & Punishment/Shootout respectively to kill him. (Loox or Vulkin with other SOULS.)
People using Kindness may want to use cards like Force of Nature and then Longevity to prevent NEO from dying if their opponent has it, but a better solution (and not just in Kindness) is by Silencing him with cards like Nacarat Jester to remove his ability.
Because of the various uses of the card, NEO can be very influential in the battlefield in terms of affecting the enemy and how they use cards as well as how you create your own deck. For those using Bravery, keep in mind that Final Charge will not work on cards such as NEO who can't attack.
Counters
If the enemy places cards like Astigmatism or Heats Flamesman, you can place down your NEO (on the required spot) in order to kill it without the need of a 2nd card.
Especially effective against Justice since it is mostly based around area damage, and Determination to lessen the chances of Hyper Goner being used.