A few weeks ago, I sent my Beasts army to fight against a freshly-undercoated Stormcast force.
We started off with the Pre-Emptive Strike scenario - a Lord-Relictor leading a vanguard of Prosecutors to secure a Realmgate and bring the rest of the legion through. Before they can get far, the Beasts get their scent and battle is joined!
To add a bit more spice we decided that, if the Lord-Relictor's summoning roll ever failed on a '1', it would accidentally bring through a Greater Daemon (picked at random, swapping sides at random - and able to summon more daemons!).