Fun mission, although it can be hard on Legendary.
My strategy for Mission 3: Relic InteriorThe overall focus in order of importance:
1. Keep your Grizzly's alive!
2. Carefully kill all the Covenant on your way in.
3. Repair the Grizzly's!
4. Don't go too fast on the way out.My general walkthrough steps:
1. Scoot in with the Grizzly's, making sure to use their
ability on any massed Covenant.
2. Let them recharge, and also use the ability separately to maximize their potential, instead of using them both at the same time.
3. Carefully work your way in to the main intersection, and eliminate the Covenant in the towers and on the ground.
4. Work your way left, blowing up everything...
5. Cross the bridge, and try to make sure if one of your Grizzly's is low on health, to have it out of danger.
6. Once across the bridge on the left side, move quickly to the middle so that you don't get rushed by too many Covenant on the left side, and blow up the attackers near Forge and Anders.
7. Have Anders repair the Grizzly's, then move everyone over to the right side light bridge so that Anders can activate it.
8. Wait out 1 minute of intensive Covenant counterattacks, and use your Grizzly's to hold the defense.
9. Once the bridge activates, be ready for Covenant to try to cross it--either deactivate the bridge so they fall to death, or concentrate firepower there to take them out.
10. Try to get your Grizzly's to cross the bridge first as they'll make short work of everything. Then cross the bridge with everyone else, and start moving everybody towards the entrance.
11. In the entrance passageway, you'll start running into a LOT of hunters. Leave your Marines and Grizzly's here, and just tell Forge and Anders to run for the objective.
12. You should win very soon as this point! Fun mission using the Grizzly's in close quarters..