What are Splicers?
Splicers are creatures introduced in New Phyrexia. Although they are not actual creature subtypes, they are always Artificers and almost always Human. Each one has a power and toughness of 1. Each makes at least one 3/3 colorless Golem artifact creature token. And each one lets Golems you control get bigger or get an ability. For example, Master Splicer has a converted mana cost of 4, is a 1/1, and makes one 3/3 Golem. Actually, it basically makes a 4/4 Golem, because it makes all Golems you have get +1/+1. That doesn't mean only the Golem it made, but other Golems like Rusted Relic and Darksteel Sentinel. Let's take another Splicer, Maul Splicer. It has a mana cost of 7, which is quite expensive, but it makes two Golems instead of just one. It also is a 1/1 and makes all Golems you have get trample! So that means it makes two 3/3 Golems with trample. Not bad, hmm?
The best Splicer is Blade Splicer, which is only 3 to cast and makes one Golem. Even though it's only 3 to cast, it makes all Golems you have get first strike! Although all Splicers are in New Phyrexia, a card similar to a Splicer is Precursor Golem, which is only 5 to cast. Unlike a Splicer, it is not a 1/1. It is a 3/3. Also, it makes two 3/3 Golems! So that's 5 mana for three 3/3's! It gets even better when whenever a player casts an instant or sorcery that targets just one golem, that player copies the spell for each Golem that it could target. So if they cast a spell that targets two golems, then this ability won't trigger. And if one of your Golems has shroud, then the spell won't copy to target it. The downside of this ability is that it works for any player, so if your opponent casts Terminate targeting one of your Golems, then you can say goodbye to all, or most, of your Golems. However, if you cast Giant Growth targeting one of your Golems, all of them will get +3/+3.
Splicers are most common in white, then green, then blue. There are no Splicers in red or black.