If i have Alhammarret's Archive, on the field and a Eternity Vessel with lets say 25 charge counters, when i play a land would i go up to 25 or 50? Does Alhammarret's Archive double effects like these?
Alhammarret’s Archive will work with Eternity Vessel, but your final life total will depend on what life you were at before the landfall trigger resolved.
When an effect like Eternity Vessel sets your life total to a specific number, it’s actually causing you to gain or lose enough life so that your life total would become that number. If you’re at 15 before the trigger resolves, then you gain 10 to go to 25 (without Archive in the picture). Alhammarret’s Archive will double the actual amount of life you gain from the trigger, so from 15 you would normally gain 10, which doubles to 20, putting you at 35. If you were at 3, you’d gain 22 but Archive doubles that to 44, putting you to 47.
I hope this all makes sense. :)