For marines, it's fairly simple. An Infantry Portal will respawn a dead marine after a 7 second delay. If a marine is dead and all powered IPs are currently spawning someone else, the marine goes into a queue.
When you are spawning, your camera moves to the IP and you can see your character model slowly materialize. If the commander activates a distress beacon, all IPs in the area immediately spawn the next marine.
For aliens, it's a bit more complicated: First, you must understand how eggs are created:
- Each hive automatically creates one egg every 4 seconds, up to a maximum of 9 per hive.
- The alien commander can create an egg near a near a Shift at the cost of 1 resource.
Aliens spawn in waves, which occurs every 13 seconds. All dead aliens (up to the number of active eggs) are randomly assigned an egg, which they spawn from 3 seconds later. The egg is destroyed.
If there are more dead players than the number of eggs, the remaining ones queue up for the next spawn wave, by which time there will (hopefully!) be more eggs around to spawn from.
The game automatically prioritizes eggs as follows:
- Eggs built by the commander are used first.
- Next, eggs near a hive that has recently taken damage are used.
- Finally, a random hive is selected.
The alien commander can spend resources to "upgrade" eggs to different lifeforms (Gorge, Fade, etc). When an alien spawns into this egg, they will spawn as that lifeform instead of a Skulk.
On top of all this, if your team has 2 or more players than the other team, you will be put into an additional queue after you die so that the number of players actually playing will be equalized. For example, in an 8v8 game, 4 people on the alien team leave. At this point, Marines will stop respawning until there are only 3 alive, when the first one to die will finally get back in the game. When you are in this queue you see a message saying, "You can respawn faster if you switch teams."