Well, I am sure this has been asked before, but I cannot find any good repository with picture/animation of simulation of colliding black hole. I can remember some about orbiting black hole but I am wondering about some other scenarios.

Let's say two black hole are on a colliding course at relativistic speed (let's say > 200 K*km/s).

1: at the closest only they even horizon intersect (even very slightly . Do they became forcibly bounded for ever even if none of the 'matter' part inside the even horizon actually enter the other's even horizon ? In other words, can events horizon escape even horizon ?

2: now the two black holes came dead on into each others. I suppose you can still consider those to have a great deal of kinetic energy. I am wondering how this tremendous amount of energy is supposed to be released. Are the gravitational wave supposed to export the energy of that impact ? I am under the impression that those wave also travel at light speed, so should not be able to escape the big flop ...

3: At speed much more 'reasonable', 3 black holes(or more) meet in convergent trajectories on a same plane (I know the odds thank you . Is it possible for those to form a orbiting triplet (are there known stars in such formation BTW ?). Eventually merging into ablack ring? Or maybe the maths forbid that ?

4: Now a smaller black hole arrive for the final dunk into that cosmic basket ... now space around that event should be weird, isn't it ?