This item has saved my ass a few times, so I want to share how it works so that others can understand how useful it is. Hope you guys find this useful 🙂
What It Does
When used, the Seed causes enemies to be hostile to all phantoms. This includes grey phantoms (members of the Bell Keeper covenant) and blue phantoms that have been summoned to defend you against a red invader. From personal experience, it seems that the effects do not end until you reset the map (use a bonfire, die, use the Aged Feather, etc.). This has a wide variety of uses. For example:
Using the Seed in the Belfry will cause the enemies to become hostile towards any invading grey phantoms. This could make the Belfries much easier to navigate.
You are watching: Seed of a tree of giants
If you are a sinner, and having a rough time getting through an area due to constant Blue Brotherhood invasions, preemptively using a Seed can make your life easier. Blue phantoms will have a harder time killing you, and they might even dispatch some enemies for you.
If you are summoning people through RSS for duels, you can keep them from running away and healing by preemptively using a Seed. Keep in mind this will effect all summons until you reset the map.
How to Find It
The Seed of a Tree of Giants is found in the Forest of the Fallen Giants, near the Soldier's Rest bonfire. This area can be accessed after defeating the Last Giant and getting the Soldier's Key. To get there from the Cardinal Tower bonfire, drop down the ladder in the bonfire room, and then (while facing the ladder) turn left. Head up the steps, and into the room on the left. This room has a locked door on the right that is opened by the Soldier's Key. After that, just follow the path. The seed itself is found hanging off the left arm of a Tree of Giants, one room away from the Soldier's Rest bonfire. The general consensus is that the Seed has a 10% chance to spawn on the tree after being invaded, with the chance increasing by 10% with every sequential invasion. For example:
If you have been invaded 3 times since you last picked up the Seed, it will have 40% percent chance to spawn the next time you are invaded.
It has been confirmed that NPC red phantoms will cause the Seed to spawn at the same rate as regular invasions. Note that Grey Phantom and RSS invasions DO NOT count towards getting the Seed.
Since the spawn rate is so high, it is extremely likely that you will have another seed ready to be picked after the third or fourth invasion, so make sure to check often.
If you are having trouble, check out this video on how to farm the Seed. Credit for the video goes to /u/Lerggio.
If anyone else has anything to add, let me know and I'll update the post. Good luck guys!