One commonly known stronghold is the one nearest to spawn, which has been thoroughly explored and mined out.
Players often leave their own mark in the End Portal chambers of strongholds through the usage of signs informing others of their visits, or the placement and destruction of blocks.
Using his superior engineering skills, noob_24 calculated the location of 38 out of the world's total 128 strongholds, with an accuracy of approximately 200-2000 blocks. These locations are written here on the wiki for the public to use, making the end more accessible, but do keep in mind that due to seed changes many of these locations may not have strongholds.
Many bases have been built around end portals however their longevity is never long lasting. Due to the fact that there were many seed changes and chunk reloads, abnormalities mean that there can be more or less end portals existent on Purity than on a regular vanilla world. Surrounding areas of spawn region end portals are nearly always completely decimated, with towering casts and waterlogged structures making the job of locating the portal itself hard, however the portal itself if always there due to the rule making the destruction/removal of end portals themselves bannable.
End portal coords that are confirmed and the closest to spawn are -1982, -266, a lavacasted tower amidst the large greater spawn ocean.
Precise End Portal reports
Various players give out precise end portal coordinates, but caution exists due to the tendency of anything with precise coordinates to be griefed or TNT trapped. Here are some reports from the field. If you visit any of these, please edit this page confirming the precise location of the end portal itself, or add the precise location and flag the previous one as inaccurate.
RobertD » the -2k portal is at exactly -1990, 32, -265 (confirmed by anihia) anihia » xaero-waypoint:End Portal:E:-1988:32:-269:2:false:0:Internal-overworld-mw$purityvanilla (confirmed by RobertD) anihia » xaero-waypoint:End Portal B:E:1214:16:-1585:2:false:0:Internal-overworld-mw$purityvanilla anihia » xaero-waypoint:E:E:-5142:26:-5701:6:false:0:Internal-overworld-mw$purityvanilla anihia » xaero-waypoint:E:E:-2065:46:4599:4:false:0:Internal-overworld-mw$purityvanilla
Eye of Ender failures
The seed to Purity Vanilla has changed twice. Most strongholds and end portals were generated under the first seed, though the existence of significant second-seed terrain within end portal range may suggest some second-seed end portals exist. Thrown Eyes of Ender direct a player to where a stronghold and end portal would be under the current and third seed, which is responsible for extremely little terrain within stronghold range of spawn, and thus almost never point to an existing stronghold. People seeking existing strongholds may read this page, look for existing nether portals correlating to approximate stronghold locations, ask other players, or, if they know the first seed, use the first seed in conjunction with version 1.13.2 of Minecraft or related programs to find existing first-seed strongholds.