Seeded runs are a great way to practice and unlock journal entries. This is a small collection of good seeds I've found.
How to Unlock Seeded Runs
I realize not everyone viewing this guide will have unlocked seeded runs, so I'll briefly explain how to do so. To start off, you want to unlock all of the characters available in the main areas. This should give you a total of 14 characters. The last 2 characters needed to unlock seeded runs can be chosen from 6 possibilities.
The easiest choice is Pilot, who can be found through trial and error from the Ice Caves shortcut in one of three places as shown in this video. Make sure to rope down so you don't take fall damage.
The next easiest choice is Guy, who is obtained from beating the normal boss. This can also be done from the Ice Caves shortcut, but you may find it advantageous to start from the beginning in order to obtain more items.
The next two choices are found in the "secret" areas of Tide Pool and Temple, which can be accessed by starting from the beginning in order to obtain the Udjat Eye, Crown/Hedjet, and Ankh (all of these are not necessarily required, but I'm keeping this guide simple).
The last two choices are available in the "secret" world. These are much harder to obtain and doing so would mean you most likely have already obtained the previously mentioned characters, so they aren't really applicable to this guide.
Once you have obtained 16 characters total, go to the place shown in this video to unlock seeded runs.
0xabacab00 (Tall Onyx Vortex)
- This is a fairly well-known seed with a jetpack+teleporter and a bomb box in the starting shop. There is a 4-3 present and altar for easy eggplant runs. It's possible to get an eggplant on 4-4 or even 5-1, but I have found no such seed yet.
0xf09e2c00 (Tall Wood Snake)
- This seed has access to paste and a lot of early bombs, as well as spike and spring shoes. This is useful for practicing skips for the drill, Olmec, lava pit, and Excalibur.
0x175081da (Cracked Onyx Vortex)
- This seed similarly has early bombs and paste. There is also a Volcana 2-3 Tun shop near Vlad's Castle with a powerpack and plasma cannon. It is possible this combination from an earlier Tun or Ghist shop, but I have found no such seed yet. The same level also has an altar on the bottom layer for easily sacrificing the pet and Vlad's hired hands to get a Kapala.
0xb0381fbf (Simple Onyx Eye)
- This seed features a starting shop with hover/jet/tele packs, a present, and an altar for practicing early eggplant runs along with Qilin skip.
0x1f01583f (Tall Onyx Ankh)
- This seed has a 1-1 teleporter for practicing speedruns without angered shopkeepers. There is also a Volcana 2-3 jetpack, but it needs to be stolen from a shopkeeper.
0x35435fdd (Smiling Onyx Vortex)
- This seed similarly has a 1-1 teleporter, but it also has a 1-2 eggplant, so it can be used to practice both speed and early eggplant runs.
0x5dbfbcce (Simple Gold Snake)
- This seed has altars on 1-2, 1-3, and Jungle 2-1 for easily getting The True Crown. It also starts with a bomb box, not that it really matters.
0x8f2edc5e, 0x51dbd6db, 0x778255f8, 0x73c1869c
- These seeds have a starting jetpack+teleporter for practicing speedruns.
- This seed has a starting jetpack which I used for practicing Qilin skip.