[militarist]

Chrispedersen you are right, you don't get +, you only negate your -.In positive (and, probably,neutral) magical enemy dominion you don't have your drain effect as well(I don't know what's happening in negative enemy dominion, would be good to check). So, you just have 0 bonus which is still worth it, as it means you got 120 points for free. And it is still better then taking M1, which becomes very expencive (because taking M1 for 40, add 120 you've lost not taking drain = 160 ).

Actually my rule is if I have weak dominion , I'm always looking towards possibility to take Drain3. Drain 3 gives you 120 points, which is almost the price of having awake pretender instead of something between sleeping/imprisoned. But it's pretty beneficial in early game, and if you like early rushes, it's not bad at all. I think with very strong sacreds, like lanka you can also try drain 3 with sleeping pretender, to maximize your points and start research after the stage early expansion. Or even with imprisoned, if you can survive early game with no magic- just start researching in enemy dominion by usual mages.
If you got turmoil in this situation or just limited in $ by any other reason, you just can maximize hiring sacreds, ignoring standard for many 1 mage per turn rule. Your sacreds, blessed so heavily definitely will do much more than mages with early spells.

Hint: water nations , even with dominion 10, always have access to enemy dominion.