Riot Games may not have planned to reveal Bel'Veth's abilities yet but they are out in the wild and now we can all see what this new Void champion does.
Bel'Veth abilities were leaked ahead of the official reveal, leaving Riot Games' planned surprise in a bit of a bind as they hoped to milk the hype in order to boost MSI 2022 viewership. It was not meant to be and all the abilities are now known, except for the actual numbers and scaling, which will likely become available on the next PBE cycle.
P: Death in Lavender
Bel'Veth's passive is somewhat similar to that of Thresh but besides minions, it also works on champions and jungle monsters who will drop Void Essence upon death. When she collects enough, Bel'Veth can activate the stack of essences to get lifesteal against monsters and send void creatures to attack a nearby tower and heal Bel'Veth.
Q - Void Surge
Bel'Veth dashes in a direction and prepares more dash charges. Dashing through enemies reduces the cooldown on top of slowing and damaging them.
W - Above and Below
Bel'Veth fires a projectiles in a straight line that damages and knocks enemies up.
E - Royal Maelstrom
This is a charged ability along the lines of Galio's taunt but Bel'Veth can't move while charging it. Instead, the ability pulls enemies towards her and then deals damage at the end of the channel.
R - Endless Banquet
The ultimate buffs Bel'Veth's basic abilities and stats. It also consumes the passive stacks to send voidlings to attack nearby champions, refreshing their power after champion takedowns.