This effect bypasses handtrap staple cards like Droll & Lock Bird or Ash Blossom & Joyous Spring that can -ironically- police the other members of the archetype
This requirement may seem elevated at first, as summoning three monsters could have proven challenging in the past
So, for example, you can Normal Summon Goldenhair, then Link it off into Salamangreat Almiraj (one of the only non-Plunder Patroll cards in the deck), and then activate Goldenhair in the Graveyard to summon it back, giving you enough material to Link Summon Blackbeard, the Plunder Patroll Captain
Artifact Color tag templates(None) Goblin Chieftain Haste (This creature can attack and as soon as it comes under your control.) Other Goblin creatures you control get +1/+1 and have haste
From a law perspective, yes, custom Magic cards are legal for personal use only