During the course of solving various lines, I have built various tablebases
to expedite the process. Originally I had only the 4-piece endgames (and
indeed, the PN-search only uses these), but then built the 5-piece for use
in the upper-level tree, and the 5-vs-K (assuming various promotion rules)
for 1. e3 e6, and 4-vs-KK (and 4-vs-KN) when solving 1. e3 c5.

Ben Nye had already built the 5-piece (for FICS rules) maybe a decade ago,

Francu has 5-piece TBs (FICS) in the DTC metric available online.

I think Ronald de Man has built a complete set of 6-piece TBs in DTZ.

On this page I list the various maximal length losses in my TBs.

On this page there is info about full-point zugzwangs.

The code I used is an adaption of the RobboBase code of "Roberto Pescatore"
that was included with the IPPOLIT project (which was probably the best freely
available TB code when I started in 2012), though I managed to lobotomise most
of the clever ideas (SMP build is gone, as is the BlockedPawn single unit).

Here is an interesting NNNNP vs K endgame. White to play takes until the
90th move for a conversion (DTC) is made. (Black wins in the end).

[FEN "3n4/1n6/n3p3/1n6/8/8/8/3K4 w - -"]
1. Ke2 N5d6 2. Kf2 N8f7 3. Kg3 Ne8 4. Kf3 Nbd8 5. Ke3 Nh8
6. Kd3 Nac7 7. Ke3 Ndf7 8. Kd3 Nh6 9. Ke3 Ng8 10. Kf3 Ng7
11. Ke3 Na6 12. Kf3 Nf7 13. Ke3 Ne8 14. Kd3 Ne7 15. Kc3 Nac7
16. Kd3 Nh6 17. Ke3 Nhg8 18. Kd3 Ng7 19. Kc3 Nf6 20. Kd3 Nh7
21. Kc3 Nge8 22. Kd3 Nf8 23. Ke3 Na6 24. Kf3 Nh7 25. Ke3 Nb8
26. Kd3 Nd7 27. Ke3 Nc8 28. Kd3 Nc7 29. Ke3 Na8 30. Kd3 Nhf8
31. Ke3 Nab6 32. Kf3 Nh7 33. Ke3 Ne7 34. Kd3 Nbc8 35. Ke3 Ng8
36. Kf3 Nce7 37. Ke3 Nh6 38. Kd3 Nc8 39. Ke3 Na7 40. Kd3 Ndf8
41. Ke3 Nf7 42. Kd3 Nd8 43. Kc3 Nd7 44. Kd3 Nc8 45. Ke3 Nb8
46. Kf3 Ne7 47. Ke3 Na6 48. Kd2 Nc7 49. Kc2 Nc8 50. Kd3 Nf8
51. Ke3 Ne8 52. Kd3 Na7 53. Kc3 Nb7 54. Kd3 Ng6 55. Ke3 Ne7
56. Kd3 Nac8 57. Ke3 Ng7 58. Kf3 Nd8 59. Ke3 Nf7 60. Kd3 Na7
61. Ke3 Nh6 62. Kf3 Nhg8 63. Kg3 Nac8 64. Kf3 Nb6 65. Ke3 Nec8
66. Kd3 Nd7 67. Ke3 Na7 68. Ke2 Nc6 69. Kf2 Nb6 70. Kf3 Nge7
71. Kg3 Nc4 72. Kg2 Nd6 73. Kg3 Nb8 74. Kf2 Nd7 75. Ke2 Nc6
76. Kd2 Nf8 77. Ke2 Ng6 78. Kf2 Nb4 79. Kg2 e5 80. Kf1 Nd5
81. Kg1 Nb7 82. Kf1 Nc5 83. Ke1 Nge6 84. Kf1 Ng5 85. Kg1 Nb3
86. Kf1 Nb4 87. Kg1 Nd4 88. Kh1 Nd3 89. Kg1 Nf2 90. Kxf2

Here is the original position (bNd8 bNb7 bNa6 bPe6 bNb5 wKd1)

Here is the position after Black's 51st move.

The White King seems to shuffle around the third rank for 50 moves, then
finally Black has been able to work-out the sliding-block puzzle of his
Knights, and at about move 70 White recedes to the 2nd rank, then loses.
Black plays e5 at move 79, but maybe could push the pawn before that.