Get Heart of Mar in weapons lab was a mission in Jak II. Ashelin Praxis gave Jak the information that Baron Praxis was meeting Krew at the weapons factory. Jak headed over there in an attempt to retrieve the Precursor Stone and stop the Baron from cracking it open.
The PlayStation 3 and Vita versions of this mission are related to a trophy named "I Heart Heart", completing this mission will reward you with a bronze trophy.
A pretty linear mission against a large amount of guards and elite guards. The Peace Maker is very useful here as it can kill multiple guards in one shot, which means if they all drop Peace Maker ammo will allow you to fire it even more without losing ammunition. After going down the elevator get rid of the first couple of guards, then press the nearby button to de-activate the electric fence. A couple more guards behind this one and then you'll find an escalator going down; shoot the nearby target reticule to make it go in reverse.
Up here you'll encounter prototype roboguards, dangerous robots that will roll around for a time until until they're hit enough times. When you do so they'll get out of their ball mode and stumble around a bit, giving you time to finish it off before it will start rolling again. The Vulcan Fury and the Blaster's wastelander moves are good to use here, though you can also stay on a nearby higher ledge to just avoid them altogether.
A nearby set of platforms will move to allow your further access, use it and kill the guards on the other side and then spin the screw here to move the platforms again. From here take the elevator up, fight some more guards and you'll find another flat escalator with some spinning blades. Use the JET-Board to get over these and jump onto another escalator behind it. At the bottom of this one shoot the marked platforms to cause them to come down, then jump onto them.
Next is another escalator (triangle shaped) with another platform you need to shoot. Do so and enter the next room filled with more guards to kill. Now you'll have to go up all the escalators slowly, shooting more target reticules to cause them to go in reverse as well as some more platforms. At the top you'll immediately be forced into a fight against more roboguards, as before rely on the Vulcan Fury and your wastelander moves.
Following this; shoot the nearby (previously under an electric fence) target reticule and go up the escalator. Up here you'll be shot at by numerous more guards, so use the Peace Maker to make easy short work of them. There's a couple more jumping to be done here involving the moving set of platforms and turning screws as well as more guards at the other side.
Finally get to the dead end at this side of the room here and use a dive punch to get through the odd panel here. You'll reach a large room down another escalator, empty at first, but as soon as you enter it you'll have to fight a huge number of roboguards. It is recommended to use the nearby barrels to just stay away from these as it is likely you'll be on low health at the last big fight in this mission.
Once you have finally destroy them all you can take the elevator to go and do the follow-up mission "Beat Krew in weapons lab".