YOU NEED GECKOLIB
This mod adds an animation after a Wither altar has been built, to make players feel more involved in the game and actually feel that a Boss Battle is about to come, instead of the boring, usual, immediate spawn of the Wither, that makes it feel useless.
(You can disable the animation with the command: "/gamerule witherSpawnAnimation false" but this won't take effect on already built altars)
Important:
-This mod is NOT compatible with "Wither Spawn Fix", but if you still want both the spawn animation and the spawn fix you can install "Wither Spawn Fix W.S.A. Compatible"
Works with Cracker's Wither Storm Mod too!
Wither Spawn Fix W.S.A. Compatible!
Excalibur resource pack compatibility! (by Ruseki)
Also try Golem Spawn Animation!
1.6.2
-fixed a bug that caused the Wither Storm (Cracker's Wither Storm Mod) to not be rendered
I realized that this is compatible with Cracker's Wither Storm Mod as well.